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59 results on '"Steinmetz M"'

1. The HETDEX Instrumentation: Hobby-Eberly Telescope Wide Field Upgrade and VIRUS

Author

Hill, GJ, Lee, H, MacQueen, PJ, Kelz, A, Drory, N, Vattiat, BL, Good, JM, Ramsey, J, Kriel, H, Peterson, T, DePoy, DL, Gebhardt, K, Marshall, JL, Tuttle, SE, Bauer, SM, Chonis, TS, Fabricius, MH, Froning, C, Haueser, M, Indahl, BL, Jahn, T, Landriau, M, Leck, R, Montesano, F, Prochaska, T, Snigula, JM, Zeimann, GR, Bryant, R, Damm, G, Fowler, JR, Janowiecki, S, Martin, J, Mrozinski, E, Odewahn, S, Rostopchin, S, Shetrone, M, Spencer, R, Mentuch Cooper, E, Armandroff, T, Bender, R, Dalton, G, Hopp, U, Komatsu, E, Lambert, D, Nocklas, H, Ramsey, LW, Roth, MM, Schneider, DP, Sneden, C, and Steinmetz, M

Subjects
Space and Planetary Science, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astronomical and Space Sciences, Astrophysics::Galaxy Astrophysics
Abstract

The Hobby-Eberly Telescope (HET) Dark Energy Experiment (HETDEX) is undertaking a blind wide-field low-resolution spectroscopic survey of 540 square degrees of sky to identify and derive redshifts for a million Lyman-alpha emitting galaxies (LAEs) in the redshift range 1.9 < z < 3.5. The ultimate goal is to measure the expansion rate of the Universe at this epoch, to sharply constrain cosmological parameters and thus the nature of dark energy. A major multi-year wide field upgrade (WFU) of the HET was completed in 2016 that substantially increased the field of view to 22 arcminutes diameter and the pupil to 10 meters, by replacing the optical corrector, tracker, and prime focus instrument package and by developing a new telescope control system. The new, wide-field HET now feeds the Visible Integral-field Replicable Unit Spectrograph (VIRUS), a new low-resolution integral field spectrograph (LRS2), and the Habitable Zone Planet Finder (HPF), a precision near-infrared radial velocity spectrograph. VIRUS consists of 156 identical spectrographs fed by almost 35,000 fibers in 78 integral field units arrayed at the focus of the upgraded HET. VIRUS operates in a bandpass of 3500-5500 Angstroms with resolving power R~800. VIRUS is the first example of large scale replication applied to instrumentation in optical astronomy to achieve spectroscopic surveys of very large areas of sky. This paper presents technical details of the HET WFU and VIRUS, as flowed-down from the HETDEX science requirements, along with experience from commissioning this major telescope upgrade and the innovative instrumentation suite for HETDEX., 65 pages, 25 figures, published in the Astronomical Journal; replaced with final published version

Published
2021
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2. MOSAIC on the ELT: high-multiplex spectroscopy to unravel the physics of stars and galaxies from the dark ages to the present-day

Author

Hammer, F, Morris, S, Cuby, JG, Kaper, L, Steinmetz, M, Afonso, J, Barbuy, B, Bergin, E, Finogenov, A, Gallego, J, Kassin, S, Miller, C, Ostlin, G, Penterricci, L, Schaerer, D, Ziegler, B, Chemla, F, Dalton, G, Frondat, FD, Evans, C, Mignant, DL, Puech, M, Rodrigues, M, Sanchez-Janssen, R, Taburet, S, Tasca, L, Yang, YB, Zanchetta, S, Dohlen, K, Dubbeldam, M, Hadi, KE, Janssen, A, Kelz, A, Larrieu, M, Lewis, I, MacIntosh, M, Morris, T, Navarro, R, Seifert, W, Laboratoire d'Astrophysique de Marseille (LAM), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

The powerful combination of the cutting-edge multi-object spectrograph MOSAIC with the world largest telescope, the ELT, will allow us to probe deeper into the Universe than was possible. MOSAIC is an extremely efficient instrument in providing spectra for the numerous faint sources in the Universe, including the very first galaxies and sources of cosmic reionization. MOSAIC has a high multiplex in the NIR and in the VIS, in addition to multi-Integral Field Units (Multi-IFUs) in NIR. As such it is perfectly suited to carry out an inventory of dark matter (from rotation curves) and baryons in the cool-warm gas phases in galactic haloes at z=3-4. MOSAIC will enable detailed maps of the intergalactic medium at z=3, the evolutionary history of dwarf galaxies during a Hubble time, the chemistry directly measured from stars up to several Mpc. Finally, it will measure all faint features seen in cluster gravitational lenses or in streams surrounding nearby galactic halos, providing MOSAIC to be a powerful instrument with an extremely large space of discoveries. The preliminary design of MOSAIC is expected to begin next year, and its level of readiness is already high, given the instrumental studies made by the team., Comment: 8 pages, 4 Figures, Pre-edited version, to appear in the ESO Messenger No.182 - Quarter 1 2021 - Version identical to the Edited one

Published
2020
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3. The Milky Way bar and bulge revealed by APOGEE DR16 and Gaia EDR3

Author

Queiroz, A. B. A., Chiappini, C., Perez-Villegas, A., Khalatyan, A., Anders, F., Barbuy, B., Santiago, B. X., Steinmetz, M., Cunha, K., Schultheis, M., Majewski, S. R., Minchev, I., Minniti, D., Beaton, R. L., Cohen, R. E., da Costa, L. N., Fernández-Trincado, J. G., Garcia-Hernández, D. A., Geisler, D., Hasselquist, S., Lane, R. R., Nitschelm, C., Rojas-Arriagada, A., Roman-Lopes, A., Smith, V., and Zasowski, G.

Subjects
Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract

We investigate the inner regions of the Milky Way with a sample of unprecedented size and coverage thanks to APOGEE DR16 and Gaia EDR3 data. Our inner Galactic sample has more than 26,000 stars within $|X_{\rm Gal}, Comment: 25 pages, 25 figures, Accepted for publication on A&A, in press

Published
2020
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4. 4MOST Consortium Survey 3: Milky Way Disc and Bulge Low-Resolution Survey (4MIDABLE-LR)

Author

Chiappini, C., Minchev, I., Starkenburg, E., Anders, F., Fusillo, N. Gentile, Gerhard, O., Guiglion, G., Khalatyan, A., Kordopatis, G., Lemasle, B., Matijevic, G., Queiroz, A. B. de Andrade, Schwope, A., Steinmetz, M., Storm, J., Traven, G., Tremblay, P. -E., Valentini, M., Andrae, R., Arentsen, A., Asplund, M., Bensby, T., Bergemann, M., Casagrande, L., Church, R., Cescutti, G., Feltzing, S., Fouesneau, M., Grebel, E. K., Kovalev, M., McMillan, P., Monari, G., Rybizki, J., Ryde, N., Rix, H. -W., Walton, N., Xiang, M., and Zucker, D.

Subjects
Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract

The mechanisms of the formation and evolution of the Milky Way are encoded in the orbits, chemistry and ages of its stars. With the 4MOST MIlky way Disk And BuLgE Low-Resolution Survey (4MIDABLE-LR) we aim to study kinematic and chemical substructures in the Milky Way disc and bulge region with samples of unprecedented size out to larger distances and greater precision than conceivable with Gaia alone or any other ongoing or planned survey. Gaia gives us the unique opportunity for target selection based almost entirely on parallax and magnitude range, hence increasing the efficiency in sampling larger Milky Way volumes with well-defined and effective selection functions. Our main goal is to provide a detailed chrono-chemo-kinematical extended map of our Galaxy and the largest Gaia follow-up down to $G = 19$ magnitudes (Vega). The complex nature of the disc components (for example, large target densities and highly structured extinction distribution in the Milky Way bulge and disc area), prompted us to develop a survey strategy with five main sub-surveys that are tailored to answer the still open questions about the assembly and evolution of our Galaxy, while taking full advantage of the Gaia data., Part of the 4MOST issue of The Messenger, published in preparation of 4MOST Community Workshop, see http://www.eso.org/sci/meetings/2019/4MOST.html

Published
2019

5. Precision Stellar Astrophysics and Galactic Archaeology: 2020

Author

Kollmeier, J., Fuller, J., Gaensicke, B., Gaudi, S., Nataf, D., Rix, H., Aerts, C., Anderson, S., Anderson, L., Anguiano, B., Basu, S., Bird, J., Brown, A., Bullock, J., Cunha, K., De Lee, N., Hekker, S., Johnson, J., Lane, R., Ness, M., Pinsonneault, M., Schwope, A., Aguirre, V., Steinmetz, M., Stevens, D., Teske, J., Tkachenko, A., Stassun, K., Ting, Y., Stutz, A., Weinberg, D., and Zasowski, G.

Subjects
Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Physics::History of Physics, Astrophysics::Galaxy Astrophysics
Abstract

This white paper is meant to capture many different elements of stellar astrophysics and galactic archaeology that highlight the important role this science will play in the 2020s era of precision astronomy.

Published
2019

6. 4MOST Consortium Survey 6: Active Galactic Nuclei

Author

Merloni, A., Alexander, D. A., Banerji, M., Boller, T., Comparat, J., Dwelly, T., Fotopoulou, S., McMahon, R., Nandra, K., Salvato, M., Croom, S., Finoguenov, A., Krumpe, M., Lamer, G., Rosario, D., Schwope, A., Shanks, T., Steinmetz, M., Wisotzki, L., and Worseck, G.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract

X-ray and mid-infrared emission are signposts of the accretion of matter onto the supermassive black holes that reside at the centres of most galaxies. As a major step towards understanding accreting supermassive black holes and their role in the evolution of galaxies, we will use the 4MOST multi-object spectrograph to provide a highly complete census of active galactic nuclei over a large fraction of the extragalactic sky observed in X-rays by eROSITA that is visible to 4MOST. We will systematically follow up all eROSITA point-like extragalactic X-ray sources (mostly active galactic nuclei), and complement them with a heavily obscured active galactic nuclei selection approach using mid-infrared data from the Wide-field Infrared Survey Explorer (WISE). The X-ray and mid-infrared flux limits of eROSITA and WISE are well matched to the spectroscopic capabilities of a 4-metre-class telescope, allowing us to reach completeness levels of ~80-90% for all X-ray selected active galactic nuclei with fluxes $f_{0.5-2\ {\rm keV}} > 10^{-14}$ erg s$^{-1}$ cm$^{-2}$; this is about a factor of 30 deeper than the ROSAT all-sky survey. With these data we will determine the physical properties (redshift, luminosity, line emission strength, masses, etc.) of up to one million supermassive black holes, constrain their cosmic evolution and clustering properties, and explore the connection between active galactic nuclei and large-scale structure over redshifts $0 \le z \le 6$., Part of the 4MOST issue of The Messenger, published in preparation of the 4MOST Community Workshop, see http://www.eso.org/sci/meetings/2019/4MOST.html

Published
2019
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7. 4MOST Consortium Survey 3: Milky Way Disc and Bulge Low-Resolution Survey (4MIDABLE-LR)

Author

Chiappini, C., Minchev, I., Starkenburg, E., Anders, F., Fusillo, N., Gerhard, O., Guiglion, G., Khalatyan, A., Kordopatis, G., Lemasle, B., Matijevic, G., Queiroz, A., Schwope, A., Steinmetz, M., Storm, J., Traven, G., Tremblay, P., Valentini, M., Andrae, R., Arentsen, A., Asplund, M., Bensby, T., Bergemann, M., Casagrande, L., Church, R., Cescutti, G., Feltzing, S., Fouesneau, M., Grebel, E., Kovalev, M., McMillan, P., Monari, G., Rybizki, J., Ryde, N., Rix, H., Walton, N., Xiang, M., Zucker, D., and Team, 4.

Subjects
Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The mechanisms of the formation and evolution of the Milky Way are encoded in the orbits, chemistry and ages of its stars. With the 4MOST MIlky way Disk And BuLgE Low-Resolution Survey (4MIDABLE-LR) we aim to study kinematic and chemical substructures in the Milky Way disc and bulge region with samples of unprecedented size out to larger distances and greater precision than conceivable with Gaia alone or any other ongoing or planned survey. Gaia gives us the unique opportunity for target selection based almost entirely on parallax and magnitude range, hence increasing the efficiency in sampling larger Milky Way volumes with well-defined and effective selection functions.

Published
2019

8. Nearly 100% of the sky is covered by Lyman-α emission around high redshift galaxies

Author

Wisotzki, L, Bacon, R, Brinchmann, J., Cantalupo, S, Richter, P, Schaye, J., Schmidt, K, Urrutia, T., Weilbacher, P, Akhlaghi, M, Bouché, N, Contini, T, Guiderdoni, B, Herenz, E, Inami, H, Kerutt, J, Leclercq, F, Marino, R, Maseda, M, Monreal-Ibero, A, Nanayakkara, T, Richard, J, Saust, R, Steinmetz, M, Wendt, M, AUTRES, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Leibniz Institute for Astrophysics Potsdam (AIP), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

International audience; Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, fed by inflows from the intergalactic medium and by outflows due to galactic winds. Absorption-line measurements along the sightlines to bright and rare background quasars indicate that this circumgalac-tic medium pervades far beyond the extent of starlight in galaxies, but very little is known about the spatial distribution of this gas. A new window into circumgalactic environments was recently opened with the discovery of ubiquitous extended Lyman-α emission from hydrogen around high-redshift galaxies[1, 2], facilitated by the extraordinary sensitivity of the MUSE instrument at the ESO Very Large Telescope[3]. Due to the faintness of this emission, such measurements were previously limited to especially favourable systems[4-6] or to massive statistical averaging[7, 8]. Here we demonstrate that low surface brightness Lyman-α emission surrounding faint galaxies at redshifts between 3 and 6 adds up to a projected sky coverage of nearly 100%. The corresponding rate of incidence (the mean number of Lyman-α emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high column density absorbers frequently detected in the spectra of distant quasars[9-12]. This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected also in emission.

Published
2018

9. Coma Berenices: first evidence for incomplete vertical phase-mixing in local velocity space with RAVE - confirmed with Gaia DR2

Author

Monari, G., Famaey, B., Minchev, I., Antoja, T., Bienayme, O., Gibson, B. K., Grebel, E. K., Kordopatis, G., McMillan, P., Navarro, J., Parker, Q. A., Quillen, A. C., Reid, W., Seabroke, G., Siebert, A., Steinmetz, M., Wyse, R. F. G., and Zwitter, T.

Subjects
Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract

Before the publication of the Gaia DR2 we confirmed with RAVE and TGAS an observation recently made with the GALAH survey by Quillen ey al. concerning the Coma Berenices moving group in the Solar neighbourhood, namely that it is only present at negative Galactic latitudes. This allowed us to show that it is coherent in vertical velocity, providing a first evidence for incomplete vertical phase-mixing. We estimated for the first time from dynamical arguments that the moving group must have formed at most ~ 1.5 Gyr ago, and related this to a pericentric passage of the Sagittarius dwarf satellite galaxy. The present note is a rewritten version of the original arXiv post on this result now also including a confirmation of our finding with Gaia DR2., Comment: AAS Research Notes

Published
2018
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10. Galactic kinematics with RAVE data

Author

Veltz, L, Bienaymé, O, Freeman, KC, Binney, J, Bland-Hawthorn, J, Gibson, BK, Gilmore, G, Grebel, EK, Helmi, A, Munari, U, Navarro, JF, Parker, QA, Seabroke, GM, Siebert, A, Steinmetz, M, Watson, FG, Williams, M, Wyse, RFG, and Zwitter, T

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We analyze the distribution of G and K type stars towards the Galactic poles using RAVE and ELODIE radial velocities, 2MASS photometric star counts, and UCAC2 proper motions. The combination of photometric and 3D kinematic data allows us to disentangle and describe the vertical distribution of dwarfs, sub-giants and giants and their kinematics. We identify discontinuities within the kinematics and magnitude counts that separate the thin disk, thick disk and a hotter component. The respective scale heights of the thin disk and thick disk are 225 ± 10 pc and 1048 ± 36 pc. We also constrain the luminosity function and the kinematic distribution function. The existence of a kinematic gap between the thin and thick disks is incompatible with the thick disk having formed from the thin disk by a continuous process, such as scattering of stars by spiral arms or molecular clouds. Other mechanisms of formation of the thick disk such as "created on the spot" or smoothly "accreted" remain compatible with our findings. © 2008 ESO.

Published
2016

11. Interstellar medium. Pseudo-three-dimensional maps of the diffuse interstellar band at 862 nm

Author

Kos, J, Zwitter, T, Wyse, R, Bienaymé, O, Binney, J, Bland-Hawthorn, J, Freeman, K, Gibson, BK, Gilmore, G, Grebel, EK, Helmi, A, Kordopatis, G, Munari, U, Navarro, J, Parker, Q, Reid, WA, Seabroke, G, Sharma, S, Siebert, A, Siviero, A, Steinmetz, M, Watson, FG, and Williams, ME

Subjects
Physics::Space Physics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The diffuse interstellar bands (DIBs) are absorption lines observed in visual and near-infrared spectra of stars. Understanding their origin in the interstellar medium is one of the oldest problems in astronomical spectroscopy, as DIBs have been known since 1922. In a completely new approach to understanding DIBs, we combined information from nearly 500,000 stellar spectra obtained by the massive spectroscopic survey RAVE (Radial Velocity Experiment) to produce the first pseudo-three-dimensional map of the strength of the DIB at 8620 angstroms covering the nearest 3 kiloparsecs from the Sun, and show that it follows our independently constructed spatial distribution of extinction by interstellar dust along the Galactic plane. Despite having a similar distribution in the Galactic plane, the DIB 8620 carrier has a significantly larger vertical scale height than the dust. Even if one DIB may not represent the general DIB population, our observations outline the future direction of DIB research.

Published
2016

12. Testing formation mechanisms of the Milky Way's thick disc with RAVE

Author

Wilson, M, Helmi, A, Morrison, HL, Breddels, MA, Bienayme, O, Binney, J, Bland-Hawthorn, J, Campbell, R, Freeman, KC, Fulbright, JP, Gibson, BK, Gilmore, G, Grebel, EK, Munari, U, Navarro, JF, Parker, QA, Reid, W, Seabroke, G, Siebert, A, Siviero, A, Steinmetz, M, Williams, MEK, Wyse, RFG, Zwitter, T, and Kapteyn Astronomical Institute

Subjects
DATA RELEASE, solar neighbourhood, Galaxy: disc, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, STELLAR MODELS, Astrophysics - Astrophysics of Galaxies, EVOLUTION, FAINT STARS, DARK-MATTER UNIVERSE, GALACTIC DISKS, Galaxy: formation, Astrophysics of Galaxies (astro-ph.GA), DISTANCE DETERMINATION, MINOR MERGERS, Astrophysics::Earth and Planetary Astrophysics, VELOCITY EXPERIMENT RAVE, Galaxy: structure, SPIRAL GALAXIES, Astrophysics::Galaxy Astrophysics
Abstract

We study the eccentricity distribution of a thick disc sample of stars observed in the Radial Velocity Experiment (RAVE) and compare it to that expected in four simulations of thick disc formation in the literature (accretion of satellites, heating of a primordial thin disc during a merger, radial migration, and gas-rich mergers), as compiled by Sales et al. (2009). We find that the distribution of our sample is peaked at low eccentricities and falls off smoothly and rather steeply to high eccentricities. This distribution is fairly robust to changes in distances, thin disc contamination, and the particular thick disc sample used. Our results are inconsistent with what is expected for the pure accretion simulation, since we find that the dynamics of local thick disc stars implies that the majority must have formed "in situ". Of the remaining models explored, the eccentricity distribution of our stars appears to be most consistent with the gas-rich merger case., Comment: 8 pages, 7 figures, submitted to MNRAS

Published
2016

13. LOFAR Low-band Antenna Observations of the 3C 295 and Boötes Fields: Source Counts and Ultra-steep Spectrum Sources

Author

Stappers, Benjamin, {van Weeren}, R J, {Williams}, W L, {Tasse}, C, {Röttgering}, H J A, {Rafferty}, D A, {van der Tol}, S, {Heald}, G, {White}, G J, {Shulevski}, A, {Best}, P, {Intema}, H T, {Bhatnagar}, S, {Reich}, W, {Steinmetz}, M, {van Velzen}, S, {En{\ss}lin}, T A, {Prandoni}, I, {de Gasperin}, F, {Jamrozy}, M, {Brunetti}, G, {Jarvis}, M J, {McKean}, J P, {Wise}, M W, {Ferrari}, C, {Harwood}, J, {Oonk}, J B R, {Hoeft}, M, {Kunert-Bajraszewska}, M, {Horellou}, C, {Wucknitz}, O, {Bonafede}, A, {Mohan}, N R, {Scaife}, A M M, {Klöckner}, H-R, {van Bemmel}, I M, {Merloni}, A, {Chyzy}, K T, {Engels}, D, {Falcke}, H, {Pandey-Pommier}, M, {Alexov}, A, {Anderson}, J, {Avruch}, I M, {Beck}, R, {Bell}, M E, {Bentum}, M J, {Bernardi}, G, {Breitling}, F, {Broderick}, J, {Brouw}, W N, {Brüggen}, M, {Butcher}, H R, {Ciardi}, B, {de Geus}, E, {de Vos}, M, {Deller}, A, {Duscha}, S, {Eislöffel}, J, {Fallows}, R A, {Frieswijk}, W, Garrett, Michael, {Grie{\ss}meier}, J, {Gunst}, A W, {Hamaker}, J P, {Hassall}, T E, {Hörandel}, J, {van der Horst}, A, {Iacobelli}, M, {Jackson}, N J, {Juette}, E, {Kondratiev}, V I, {Kuniyoshi}, M, {Maat}, P, {Mann}, G, {McKay-Bukowski}, D, {Mevius}, M, {Morganti}, R, {Munk}, H, {Offringa}, A R, {Orrù}, E, {Paas}, H, {Pandey}, V N, {Pietka}, G, {Pizzo}, R, {Polatidis}, A G, {Renting}, A, {Rowlinson}, A, {Schwarz}, D, {Serylak}, M, {Sluman}, J, {Smirnov}, O, {Stappers}, B W, {Stewart}, A, {Swinbank}, J, {Tagger}, M, {Tang}, Y, {Thoudam}, S, {Toribio}, C, {Vermeulen}, R, {Vocks}, C, {Zarka}, P, Astronomy, Netherlands Institute for Radio Astronomy (ASTRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], SKA South Africa, Ska South Africa, Rhodes University, Grahamstown, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, SLAC National Accelerator Laboratory (SLAC), Stanford University, University of Edinburgh, Department of Computer Science and Automation [Bangalore] (CSA), Indian Institute of Science [Bangalore] (IISc Bangalore), Max-Planck-Institut für Radioastronomie (MPIFR), Charles Darwin University, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Thüringer Landessternwarte Tautenburg (TLS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Jacobs University [Bremen], School of Physics and Astronomy [Southampton], University of Southampton, Radboud university [Nijmegen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Leibniz-Institut für Astrophysik Potsdam (AIP), SRON Netherlands Institute for Space Research (SRON), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medstar Research Institute, Institute of Mathematical and Physical Sciences, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Ruhr-Universität Bochum [Bochum], University of Oulu, Applied Stochastics (IMAPP), Oxford Astrophysics, University of Oxford [Oxford], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, ANR-09-JCJC-0001,OPALES(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Van Weeren, R.J., Williams, W.L., Tasse, C., Röttgering, H.J.A., Rafferty, D.A., Van Der Tol, S., Heald, G., White, G.J., Shulevski, A., Best, P., Intema, H.T., Bhatnagar, S., Reich, W., Steinmetz, M., Van Velzen, S., Enßlin, T.A., Prandoni, I., De Gasperin, F., Jamrozy, M., Brunetti, G., Jarvis, M.J., McKean, J.P., Wise, M.W., Ferrari, C., Harwood, J., Oonk, J.B.R., Hoeft, M., Kunert-Bajraszewska, M., Horellou, C., Wucknitz, O., Bonafede, A., Mohan, N.R., Scaife, A.M.M., Klöckner, H.-R., Van Bemmel, I.M., Merloni, A., Chyzy, K.T., Engels, D., Falcke, H., Pandey-Pommier, M., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Bentum, M.J., Bernardi, G., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., De Geus, E., De Vos, M., Deller, A., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Hörandel, J., Van Der Horst, A., Iacobelli, M., Jackson, N.J., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Maat, P., Mann, G., McKay-Bukowski, D., Mevius, M., Morganti, R., Munk, H., Offringa, A.R., Orrù, E., Paas, H., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Renting, A., Rowlinson, A., Schwarz, D., Serylak, M., Sluman, J., Smirnov, O., Stappers, B.W., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Zarka, P., Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), general, surveys [radio continuum], EWI-25425, Radio galaxy, Astronomy, techniques, galaxies: active, radio continuum: general, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, METIS-309728, surveys, survey, Source counts, Astrophysics::Galaxy Astrophysics, Physics, Spectral index, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, BOOTES, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Redshift, interferometric [techniques], IR-93230, Space and Planetary Science, [SDU]Sciences of the Universe [physics], techniques: interferometric, Astrophysics of Galaxies (astro-ph.GA), interferometric, active [galaxies], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Spectral energy distribution, general [radio continuum], Noise (radio), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We present LOFAR Low Band observations of the Bootes and 3C295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam$^{-1}$, making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17 to 52 deg$^{2}$. From the observations we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and VLA 74 MHz differential source counts, scaling with a spectral index of $-0.7$. We find that a spectral index scaling of $-0.5$ is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens towards lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum ($\alpha < -1.1$) radio sources, that could be associated with massive high redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz and 1.4 GHz for sources in the Bo\"otes field. We cross-correlate these radio sources with optical and infrared catalogues and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the $ 0.7 \lesssim z \lesssim 2.5$ range., Comment: 26 pages, 20 figures, ApJ in press

Published
2014

14. Wide-field LOFAR imaging of the field around the double-double radio galaxy B1834+620

Author

Orrù, E, Van Velzen, S, Pizzo, R. F., Yatawatta, S, Paladino, R, Iacobelli, M, Murgia, M, Falcke, H, Morganti, R, De Bruyn, A. G., Ferrari, C, Anderson, J, Bonafede, A, Mulcahy, D, Asgekar, A, Avruch, I. M., Beck, R, Bell, M.E., Van Bemmel, I, Bentum, M. J., Bernardi, G, Best, P, Breitling, F, Brüggen, M, Broderick, J.W., Ciardi, B, Corstanje, A, Conway, J. E., De Geus, E, Butcher, H. R., Ciardi, B., Deller, A, Duscha, S, Eislöffel, J, Engels, D, Frieswijk, W, Grießmeier, Jean-Mathias, Heald, G, Hoeft, M, Intema, H, Juette, E, Kohler, J, Kuniyoshi, M, Kuper, G, Loose, M, Maat, P, Mann, G, Markoff, S, Mcfadden, R, Mckay-Bukowski, D, Miley, G, Moldon, J, Molenaar, G, Munk, H, Nelles, A, Paas, H, Pandey-Pommier, M, Pietka, G, Reich, W, Röttgering, H, Rowlinson, A, Scaife, A, Schoenmakers, A, Schwarz, D., Serylak, M, Shulevski, A, Smirnov, O, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, Michel, Tasse, C., Thoudam, S, Toribio, M.C, Vermeulen, R, Vocks, C, Van Weeren, R.J., Wijers, R.A.M.J, Wise, M.W., Wucknitz, O, Netherlands Institute for Radio Astronomy (ASTRON), INAF - Osservatorio Astronomico di Bologna (OABO), Istituto Nazionale di Astrofisica (INAF), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Institute for Nanostructured Materials (CNR-ISMN), Consiglio Nazionale delle Ricerche (CNR), Radboud university [Nijmegen], Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Département de Géologie, Université de Montréal (UdeM), University of Hamburg, Jacobs University [Bremen], University of Southampton, SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Medstar Research Institute, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Ruhr-Universität Bochum [Bochum], Karlsruhe Institute of Technology (KIT), Max-Planck-Institut für Radioastronomie (MPIFR), Queen's Medical Centre, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Anton Pannekoek Institute for Astronomy, Center for Information Technology CIT, Université de Groningen, Université de Montréal [Montréal], Deutsches GeoForschungsZentrum GFZ, Department Geodesy and Remote Sensing, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden, National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Radboud University [Nijmegen], and Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Radiation mechanisms: non-thermal, techniques: interferometric, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxies: active, Astroparticle physics, Astrophysics::Galaxy Astrophysics, Radio continuum: galaxies, Instrumentation:interferometers
Abstract

International audience; Context. The existence of double-double radio galaxies (DDRGs) is evidence for recurrent jet activity in AGN, as expected from standard accretion models. A detailed study of these rare sources provides new perspectives for investigating the AGN duty cycle, AGN-galaxy feedback, and accretion mechanisms. Large catalogues of radio sources, on the other hand, provide statistical information about the evolution of the radio-loud AGN population out to high redshifts.Aims. Using wide-field imaging with the LOFAR telescope, we study both a well-known DDRG as well as a large number of radio sources in the field of view. Methods. We present a high resolution image of the DDRG B1834+620 obtained at 144 MHz using LOFAR commissioning data. Our image covers about 100 square degrees and contains over 1000 sources.Results. The four components of the DDRG B1834+620 have been resolved for the first time at 144 MHz. Inner lobes were found to point towards the direction of the outer lobes, unlike standard FR II sources. Polarized emission was detected at +60 rad m −2 in the northern outer lobe. The high spatial resolution allows the identification of a large number of small double-lobed radio sources; roughly 10% of all sources in the field are doubles with a separation smaller than 1.Conclusions. The spectral fit of the four components is consistent with a scenario in which the outer lobes are still active or the jets recently switched off, while emission of the inner lobes is the result of a mix-up of new and old jet activity. From the presence of the newly extended features in the inner lobes of the DDRG, we can infer that the mechanism responsible for their formation is the bow shock that is driven by the newly launched jet. We find that the density of the small doubles exceeds the density of FR II sources with similar properties at 1.4 GHz, but this difference becomes smaller for low flux densities. Finally, we show that the significant challenges of wide-field imaging (e.g., time and frequency variation of the beam, directional dependent calibration errors) can be solved using LOFAR commissioning data, thus demonstrating the potential of the full LOFAR telescope to discover millions of powerful AGN at redshift z ∼ 1.

Published
2015

15. Young [$��$/Fe]-enhanced stars discovered by CoRoT and APOGEE: What is their origin?

Author

Chiappini, C., Anders, F., Rodrigues, T. S., Miglio, A., Montalban, J., Mosser, B., Girardi, L., Valentini, M., Noels, A., Morel, T., Minchev, I., Steinmetz, M., Santiago, B. X., Schultheis, M., Martig, M., da Costa, L. N., Maia, M. A. G., Prieto, C. Allende, Peralta, R. de Assis, Hekker, S., Theme��l, N., Kallinger, T., Garcia, R. A., Mathur, S., Baudin, F., Beers, T. C., Cunha, K., Harding, P., Holtzman, J., Majewski, S., Meszaros, Sz., Nidever, D., Pan, K., Schiavon, R. P., Shetrone, M. D., Schneider, D. P., and Stassun, K.

Subjects
Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

We report the discovery of a group of apparently young CoRoT red-giant stars exhibiting enhanced [alpha/Fe] abundance ratios (as determined from APOGEE spectra) with respect to Solar values. Their existence is not explained by standard chemical evolution models of the Milky Way, and shows that the chemical-enrichment history of the Galactic disc is more complex. We find similar stars in previously published samples for which isochrone-ages could be robustly obtained, although in smaller relative numbers, which could explain why these stars have not received prior attention. The young [alpha/Fe]-rich stars are much more numerous in the CoRoT-APOGEE (CoRoGEE) inner-field sample than in any other high-resolution sample available at present, as only CoRoGEE can explore the inner-disc regions and provide ages for its field stars. The kinematic properties of the young [$��$/Fe]-rich stars are not clearly thick-disc like, despite their rather large distances from the Galactic mid-plane. Our tentative interpretation of these and previous intriguing observations in the Milky Way is that these stars were formed close to the end of the Galactic bar, near corotation -- a region where gas can be kept inert for longer times, compared to other regions shocked more frequently by the passage of spiral arms. Moreover, that is where the mass return from older inner-disc stellar generations should be maximal (according to an inside-out disc-formation scenario), further diluting the in-situ gas. Other possibilities to explain these observations (e.g., a recent gas-accretion event) are also discussed., Letter in press in Astronomy and Astrophysics (5 pages, 4 figures + 2 pages Appendix)

Published
2015
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16. VizieR Online Data Catalog: RAVE 4th data release (Kordopatis+, 2013)

Author

Kordopatis, G., Gilmore, G., Steinmetz, M., Boeche, C., Seabroke, G. M., Siebert, A., Zwitter, T., Binney, J., de Laverny, P., Recio-Blanco, A., Williams, M. E. K., Piffl, T., Enke, H., Roeser, S., Bijaoui, A., Wyse, R. F. G., Freeman, K., Munari, U., Carrillo, I., Anguiano, B., Burton, D., Campbell, R., Cass, C. J. P., Fiegert, K., Hartley, M., Parker, Q. A., Reid, W., Ritter, A., Russell, K. S., Stupar, M., Watson, F. G., Bienayme, O., Bland-Hawthorn, J., Gerhard, O., Gibson, B. K., Grebel, E. K., Helmi, A., Navarro, J. F., Conrad, C., Famaey, B., Faure, C., Just, A., Kos, J., Matijevic, G., McMillan, P. J., Minchev, I., Scholz, R., Sharma, S., Siviero, A., Wylie de Boer, E., Zerjal, M., Astronomy, and Physics of Nanodevices

Subjects
Milky Way, Photometry, Radial velocities, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Surveys, Stars: fundamental, Astrophysics::Galaxy Astrophysics, Physics::Geophysics
Abstract

Spectroscopic radial velocities for 425,561 stars in the Milky-Way southern hemisphere using the 6dF instrument at the AAO. Targets new to this release are drawn from a new input catalog based on the I magnitude from the DENIS point source catalog. The spectroscopic observations are made in the Calcium triplet region at a resolution of ~7,500. (1 data file).

Published
2014

17. DIFFUSE INTERSTELLAR BAND AT 8620 \ufffd IN RAVE: A NEW METHOD FOR DETECTING THE DIFFUSE INTERSTELLAR BAND IN SPECTRA OF COOL STARS

Author

Kos, J., Zwitter, T., Grebel, E. K., Bienayme, O., Binney, J., Bland-Hawthorn, J., Freeman, K. C., Gibson, B. K., Gilmore, G., Kordopatis, G., Navarro, J. F., Parker, Q., Reid, W. A., Seabroke, G., Siebert, A., Siviero, A., Steinmetz, M., Watson, F., and Wyse, R. F. G.

Subjects
Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Diffuse interstellar bands are usually observed in spectra of hot stars, where interstellar lines are rarely blended with stellar ones. The need for hot stars is a strong limitation in the number of sightlines we can observe and the distribution of sightlines in the Galaxy, as hot stars are rare and concentrated in the Galactic plane. We are introducing a new method, where interstellar lines can be observed in spectra of cool stars in large spectroscopic surveys. The method is completely automated and does not require prior knowledge of the stellar parameters. If known, the stellar parameters only reduce the computational time and are not involved in the extraction of the interstellar spectrum. The main step in extracting interstellar lines is a construction of the stellar spectrum, which is in our method done by finding other observed spectra that lack interstellar features and are otherwise very similar to the spectrum in question. Such spectra are then combined into a single stellar spectrum template, which matches the stellar component in an observed spectrum. We demonstrate the performance of this new method on a sample of 482,430 spectra observed in RAVE survey. However, many spectra have to be combined (48 on average) in order to achieve a S/N ratio high enough to measure the DIB's profile, hence limiting the spatial information about the ISM. Only one strong interstellar line is included in the RAVE spectral range, a diffuse interstellar band at 8620 ��. We compare its equivalent width with extinction maps and with Bayesian reddening, calculated for individual stars, and provide a linear relation between the equivalent width and reddening. Separately from the introduced method, we calculate equivalent widths of the diffuse interstellar band in spectra of hot stars with known extinction and compare all three linear relations with each other and with relations from the literature., 12 pages, 10 figures, submitted to ApJ

Published
2013

18. Chromospherically Active Stars in the RAVE Survey. I. The Catalogue

Author

��erjal, M., Zwitter, T., Matijevi��, G., Strassmeier, K. G., Bienaym��, O., Bland-Hawthorn, J., Boeche, C., Freeman, K. C., Grebel, E. K., Kordopatis, G., Munari, U., Navarro, J. F., Parker, Q. A., Reid, W., Seabroke, G., Siviero, A., Steinmetz, M., and Wyse, R. F. G.

Subjects
Astrophysics - Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract

RAVE, the unbiased magnitude limited survey of the southern sky stars, contained 456,676 medium-resolution spectra at the time of our analysis. Spectra cover the CaII IRT range which is a known indicator of chromospheric activity. Our previous work (Matijevi\v{c} et al. 2012) classified all spectra using locally linear embedding. It identified 53,347 cases with a suggested emission component in calcium lines. Here we use a spectral subtraction technique to measure the properties of this emission. Synthetic templates are replaced by the observed spectra of non-active stars to bypass the difficult computations of non-LTE profiles of the line cores and stellar parameter dependence. We derive both the equivalent width of the excess emission for each calcium line on a 5\AA\ wide interval and their sum EW_IRT for ~44,000 candidate active dwarf stars with S/N>20 and with no respect to the source of their emission flux. From these ~14,000 show a detectable chromospheric flux with at least 2\sigma\ confidence level. Our set of active stars vastly enlarges previously known samples. Atmospheric parameters and in some cases radial velocities of active stars derived from automatic pipeline suffer from systematic shifts due to their shallower calcium lines. We re-estimate the effective temperature, metallicity and radial velocities for candidate active stars. The overall distribution of activity levels shows a bimodal shape, with the first peak coinciding with non-active stars and the second with the pre main-sequence cases. The catalogue will be publicly available with the next RAVE public data releases., Comment: 13 pages, 9 figures

Published
2013

19. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author

Asgekar, A., Oonk, J.B., Yatawatta, S., Weeren, R.J., McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, Michael, Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Braun, R., Breitling, F., Brink, R.H., Broderick, J.W., Brouw, W.N., Brüggen, M., Butcher, H.R., Cappellen, W., Ciardi, B., Conway, J.E., De Gasperin, F., Geus, E., Jong, A., Vos, M., Duscha, S., Eislöffel, J., Falcke, H., Fellows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C.J., Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevins, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, Varun, Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Scheers, Bart, Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C.A., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, Ralph, Wise, Michael, Wucknitz, O., Zarka, P., Leeuwen, Joeri, and Database Architectures

Subjects
ISM: clouds - radio lines: ISM – ISM: individual objects: Cassiopeia A, Astrophysics::Galaxy Astrophysics
Abstract

Cassiopeia A was observed using the low-band antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of >5 from two independent LOFAR data sets. The derived line velocities (vLSR ~ - 50 km s-1) and integrated optical depths (~13 s-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR data set and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 percent) integrated optical depths, indicating that there is small-scale angular structure of the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 × 10-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band.

Published
2013

20. Studying Galactic interstellar turbulence through fluctuations in synchrotron emission

Author

Iacobelli, M., Haverkorn, M., Orrú, E., Pizzo, R. F., Anderson, J., Beck, R., Bell, M. R., Bonafede, A., Chyzy, K., Dettmar, R.-J., Enßlin, T. A., Heald, G., Horellou, C., Horneffer, A., Jurusik, W., Junklewitz, H., Kuniyoshi, M., Mulcahy, D. D., Paladino, R., Reich, W., Scaife, A., Sobey, C., Sotomayor-Beltran, C., Alexov, A., Asgekar, A., Avruch, I. M., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bırzan, L., Breitling, F., Broderick, J., Brouw, W. N., Brüggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., de Gasperin, F., de Geus, E., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R. A., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Gunst, A. W., Hamaker, J. P., Hassall, T. E., Hessels, J. W. T., Hoeft, M., Hörandel, J., Jelic, V., Karastergiou, A., Kondratiev, V. I., Koopmans, L. V. E., Kramer, M., Kuper, G., van Leeuwen, J., Macario, G., Mann, G., McKean, J. P., Munk, H., Pandey-Pommier, M., Polatidis, A. G., Röttgering, H., Schwarz, Dominik, Sluman, J., Smirnov, O., Stappers, B. W., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Vogt, C., van Weeren, R. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., Leiden Observatory [Leiden], Universiteit Leiden, Netherlands Institute for Radio Astronomy (ASTRON), Radboud University [Nijmegen], Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Jacobs University [Bremen], Uniwersytet Jagielloński w Krakowie = Jagiellonian University (UJ), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO), School of Physics and Astronomy [Southampton], University of Southampton, Sydney Institute for Astronomy (SIfA), The University of Sydney, SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Oxford Astrophysics, University of Oxford, Université de Nice Sophia-Antipolis (UNSA), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universität Bielefeld, Rhodes University, Grahamstown, SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), This work is part of the research programme 639.042.915, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO)., European Project: 239490,EC:FP7:PEOPLE,FP7-PEOPLE-IRG-2008,MAGNETIC_MILKYWAY(2009), Universiteit Leiden [Leiden], Radboud university [Nijmegen], Harvard University [Cambridge]-Smithsonian Institution, Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Galaxy, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], astronomical techniques, synchrotron radiation, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, interstellar matter, cosmic ray propagation, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], Astrophysics::Galaxy Astrophysics
Abstract

International audience; Aims: The characteristic outer scale of turbulence (i.e. the scale at which the dominant source of turbulence injects energy to the interstellar medium) and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters.Methods: We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l,b) ~ (137.0°, +7.0°) at 80' × 70' resolution in the range [146, 174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations.Results: We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum displays a power law behaviour for scales between 100 and 8 arcmin with a slope α = -1.84 ± 0.19. We find an upper limit of ~20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region, which is in agreement with previous estimates in literature. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes.Conclusions. We present the first LOFAR detection and imaging of the Galactic diffuse synchrotron emission around 160 MHz from the highly polarized Fan region. The power spectrum of the foreground synchrotron fluctuations is approximately a power law with a slope α ≈ -1.84 up to angular multipoles of ≤1300, corresponding to an angular scale of ~8 arcmin. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence (Lout) of the Galactic synchrotron foreground, finding a range of plausible values of 10-20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates.

Published
2013

21. C IV Absorption from Galaxies in the Process of Formation

Author

Martin Haehnelt, Steinmetz, M., and Rauch, M.

Subjects
Physics, Range (particle radiation), Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Galaxy, Spectral line, Redshift, Space and Planetary Science, Metal absorption, Galaxy formation and evolution, Impact parameter, Hydrogen absorption, Astrophysics::Galaxy Astrophysics
Abstract

We investigate the heavy element QSO absorption systems caused by gas condensations at high redshift which evolve into galaxies with circular velocity of 100 to 200 km/s at the present epoch. Artificial QSO spectra were generated for a variety of lines-of-sight through regions of the universe simulated with a hydrodynamics code. The CIV and HI absorption features in these spectra closely resemble observed CIV and HI absorption systems over a wide range in column density. CIV absorption complexes with multiple-component structure and velocity spreads up to about 600 km/s are found. The broadest systems are caused by lines-of-sight passing through groups of protogalactic clumps with individual velocity dispersions of less than 150 km/s aligned along filamentary structures. The temperature of most of the gas does not take the photoionization equilibrium value. This invalidates density and size estimates derived from thermal equilibrium models. Consequences for metal abundance determinations are briefly discussed. We predict occasional exceptionally large ratios of CIV to HI column density (up to a third) for lines-of-sight passing through compact halos of hot gas with temperature close to 3 10^5 K. Our model may be able to explain both high-ionization multi-component heavy-element absorbers and damped Lyman alpha systems as groups of small protogalactic clumps., 13 pages, uuencoded postscript file, 4 figures included submitted to ApJ (Letters); complete version also available at http://www.mpa-garching.mpg.de/Galaxien/prep.html

Published
1996

22. Kinematic groups beyond the Solar neighbourhood with RAVE

Author

Antoja, T., Helmi, A., Bienayme, O., Bland-Hawthorn, J., Famaey, B., Freeman, K., Gibson, B. K., Gilmore, G., Grebel, E. K., Minchev, I., Munari, U., Navarro, J., Parker, Q., Reid, W., Seabroke, G. M., Siebert, A., Siviero, A., Steinmetz, M., Williams, M., Wyse, R., Zwitter, T., Astronomy, and Kapteyn Astronomical Institute

Subjects
Galaxy: evolution, DATA RELEASE, solar neighbourhood, FOS: Physical sciences, DISC, Astrophysics - Astrophysics of Galaxies, BAR, GALACTIC STRUCTURE, HIPPARCOS, Astrophysics of Galaxies (astro-ph.GA), GIANTS, SPACE, STREAMS, Astrophysics::Earth and Planetary Astrophysics, VELOCITY EXPERIMENT RAVE, Galaxy: kinematics and dynamics, Galaxy: structure, NEARBY STARS, Astrophysics::Galaxy Astrophysics
Abstract

We analyse the kinematics of disc stars observed by the RAVE survey in and beyond the Solar neighbourhood.We detect significant overdensities in the velocity distributions using a technique based on the wavelet transform.We find that the main local kinematic groups are large scale features, surviving at least up to ~1 kpc from the Sun in the direction of anti-rotation, and also at ~700 pc below the Galactic plane.We also find that for regions located at different radii than the Sun, the known groups appear shifted in the velocity plane. For example, the Hercules group has a larger azimuthal velocity for regions inside the Solar circle and a lower value outside. We have also discovered a new group at (U, V) = (92,-22) km/s in the Solar neighbourhood and confirmed the significance of other previously found groups. Some of these trends detected for the first time are consistent with dynamical models of the effects of the bar and the spiral arms. More modelling is required to definitively characterise the non-axisymmetric components of our Galaxy using these groups., Minor changes to match the accepted version in MNRAS Letters

Published
2012

23. The properties of the local spiral arms from RAVE data: two-dimensional density wave approach

Author

Siebert, A., Famaey, B., Binney, J., Burnett, B., Faure, C., Minchev, I., Williams, M. E. K., Bienayme, O., Bland-Hawthorn, J., Boeche, C., Gibson, B. K., Grebel, E. K., Helmi, A., Just, A., Munari, U., Navarro, J. F., Parker, Q. A., Reid, W. A., Seabroke, G., Siviero, A., Steinmetz, M., Zwitter, T., and Astronomy

Subjects
SOLAR NEIGHBORHOOD, stars: kinematics and dynamics, DATA RELEASE, MODELS, FOS: Physical sciences, DISK GALAXIES, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxy: fundamental parameters, RESONANCE, Astrophysics - Astrophysics of Galaxies, Astrophysics of Galaxies (astro-ph.GA), MILKY-WAY, M81, Astrophysics::Earth and Planetary Astrophysics, KINEMATICS, VELOCITY EXPERIMENT RAVE, Galaxy: kinematics and dynamics, STARS, Astrophysics::Galaxy Astrophysics
Abstract

Using the RAVE survey, we recently brought to light a gradient in the mean galactocentric radial velocity of stars in the extended solar neighbourhood. This gradient likely originates from non-axisymmetric perturbations of the potential, among which a perturbation by spiral arms is a possible explanation. Here, we apply the traditional density wave theory and analytically model the radial component of the two-dimensional velocity field. Provided that the radial velocity gradient is caused by relatively long-lived spiral arms that can affect stars substantially above the plane, this analytic model provides new independent estimates for the parameters of the Milky Way spiral structure. Our analysis favours a two-armed perturbation with the Sun close to the inner ultra-harmonic 4:1 resonance, with a pattern speed \Omega_p=18.6^{+0.3}_{-0.2} km/s/kpc and a small amplitude A=0.55 \pm 0.02% of the background potential (14% of the background density). This model can serve as a basis for numerical simulations in three dimensions, additionally including a possible influence of the galactic bar and/or other non-axisymmetric modes., Comment: 9 pages, 4 figures, accepted for publication in MNRAS

Published
2012
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24. Disc heating: comparing the Milky Way with cosmological simulations

Author

House, E. L., Brook, C. B., Gibson, B. K., Sánchez-Blázquez, Patricia, Courty, S., Few, C. G., Governato, F., Kawata, D., Roškar, R., Steinmetz, M., Stinson, G. S., Teyssier, R., University of Zurich, House, E L, and UAM. Departamento de Física Teórica

Subjects
530 Physics, Galaxy: disc, Galaxies: evolution, Física, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxies: formation, evolution [Galaxies], formation [Galaxies], disc [Galaxy], 1912 Space and Planetary Science, 10231 Institute for Computational Science, 3103 Astronomy and Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2011 RAS © The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved., We present an analysis of a suite of simulations run with different particle- and grid-based cosmological hydrodynamical codes and compare them with observational data of the Milky Way. This is the first study to make comparisons of properties of galaxies simulated with particle- and grid-based codes. Our analysis indicates that there is broad agreement between these different modelling techniques. We study the velocity dispersion-age relation for disc stars at z= 0 and find that four of the simulations are more consistent with observations by Holmberg, Nordstroem & Andersen in which the stellar disc appears to undergo continual/secular heating. Two other simulations are in better agreement with the Quillen & Garnett observations that suggest 'saturation' in the heating profile for young stars in the disc. None of the simulations has thin discs as old as that of the Milky Way. We also analyse the kinematics of disc stars at the time of their birth for different epochs in the galaxies' evolution and find that in some simulations old stars are born cold within the disc and are subsequently heated, while other simulations possess old stellar populations which are born relatively hot. The models which are in better agreement with observations of the Milky Way's stellar disc undergo significantly lower minor-merger/assembly activity after the last major merger, that is, once the disc has formed. All of the simulations are significantly 'hotter' than the Milky Way disc; on top of the effects of mergers, we find a 'floor' in the dispersion that is related to the underlying treatment of the heating and cooling of the interstellar medium, and the low density threshold which such codes use for star formation. This finding has important implications for all studies of disc heating that use hydrodynamical codes, ELH acknowledges the support of the UK’s Science & Technology Facilities Council through its PhD studentship programme (ST/F006764/1). BKG and CBB acknowledge the support of the UK’s Science & Technology Facilities Council (ST/F002432/1). PS-B acknowledges the support of a Marie Curie European Reintegration grant within the Sixth European Community Framework Programme. FG acknowledges the support from the HST GO-1125, NSF AST-0607819 and NASA ATP NNX08AG84G grants. RT would like to thank the granted access to the HPC resources of CINES and CCRT under the allocations 2009-SAP2191 and 2010-GEN2192 made by GENCI.We thank the DEISA consortium, co-funded through EU FP6 project RI-031513 and the FP7 project RI-222919, for support within the DEISA Extreme Computing Initiative

Published
2011

25. The dark matter assembly of the Local Group in constrained cosmological simulations of a LambdaCDM universe

Author

Forero-Romero, J. E., Hoffman, Y., Yepes, G., Gottoeber, S., Piontek, R., Klypin, A., and Steinmetz, M.

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We make detailed theoretical predictions for the assembly properties of the Local Group (LG) in the standard LambdaCDM cosmological model. We use three cosmological N-body dark matter simulations from the CLUES project, which are designed to reproduce the main dynamical features of the matter distribution down to the scale of a few Mpc around the LG. Additionally, we use the results of an unconstrained simulation with a sixty times larger volume to calibrate the influence of cosmic variance. We characterize the Mass Aggregation History (MAH) for each halo by three characteristic times, the formation, assembly and last major merger times. A major merger is defined by a minimal mass ratio of 10:1. We find that the three LGs share a similar MAH with formation and last major merger epochs placed on average \approx 10 - 12 Gyr ago. Between 12% and 17% of the halos in the mass range 5 x 10^11 Msol/h < M_h < 5 x 10^12 Msol/h have a similar MAH. In a set of pairs of halos within the same mass range, a fraction of 1% to 3% share similar formation properties as both halos in the simulated LG. An unsolved question posed by our results is the dynamical origin of the MAH of the LGs. The isolation criteria commonly used to define LG-like halos in unconstrained simulations do not narrow down the halo population into a set with quiet MAHs, nor does a further constraint to reside in a low density environment. The quiet MAH of the LGs provides a favorable environment for the formation of disk galaxies like the Milky Way and M31. The timing for the beginning of the last major merger in the Milky Way dark matter halo matches with the gas rich merger origin for the thick component in the galactic disk. Our results support the view that the specific large and mid scale environment around the Local Group play a critical role in shaping its MAH and hence its baryonic structure at present., 11 pages, 4 figures. Accepted for publication in MNRAS

Published
2011
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26. Local Stellar Kinematics From Rave Data - I. Local Standard Of Rest

Author

Coskunoglu, B., Ak, S., Bilir, S., Karaali, S., Yaz, E., Gilmore, G., Seabroke, G. M., Bienayme, O., Bland-Hawthorn, J., Campbell, R., Freeman, K. C., Gibson, B., Grebel, E. K., Munari, U., Navarro, J. F., Parker, Q. A., Siebert, A., Siviero, A., Steinmetz, M., and Watson, F. G.

Subjects
Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We analyse a sample of 82 850 stars from the RAdial Velocity Experiment (RAVE) survey, with well-determined velocities and stellar parameters, to isolate a sample of 18 026 high-probability thin-disc dwarfs within 600 pc of the Sun. We derive space motions for these stars, and deduce the solar space velocity with respect to the local standard of rest. The peculiar solar motion we derive is in excellent agreement in radial U-circle dot and vertical W-circle dot peculiar motions with other recent determinations. Our derived tangential peculiar velocity, V-circle dot, agrees with very recent determinations, which favour values near 13 km s-1, in disagreement with earlier studies. The derived values are not significantly dependent on the comparison sample chosen, or on the method of analysis. The local Galaxy seems very well dynamically relaxed, in a near symmetric potential.

Published
2011

27. Local Stellar Kinematics from RAVE Data: I. Local Standard of Rest

Author

Coskunoglu, B., Ak, S., Bilir, S., Karaali, S., Yaz, E., Gilmore, G., Seabroke, G. M., Bienayme, O., Bland-Hawthorn, J., Campbell, R., Freeman, K. C., Gibson, B., Grebel, E. K., Munari, U., Navarro, J. F., Parker, Q. A., Siebert, A., Siviero, A., Steinmetz, M., Watson, F. G., Wyse, R. F. G., and Zwitter, T.

Subjects
Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract

We analyze a sample of 82850 stars from the RAVE survey, with well-determined velocities and stellar parameters, to isolate a sample of 18026 high-probability thin-disc dwarfs within 600 pc of the Sun. We derive space motions for these stars, and deduce the solar space velocity with respect to the Local Standard of Rest. The peculiar solar motion we derive is in excellent agreement in radial $U_{\odot}$ and vertical $W_{\odot}$ peculiar motions with other recent determinations. Our derived tangential peculiar velocity, $V_{\odot}$ agrees with very recent determinations, which favour values near 13 km s$^{-1}$, in disagreement with earlier studies. The derived values are not significantly dependent on the comparison sample chosen, or on the method of analysis. The local galaxy seems very well dynamically relaxed, in a near symmetric potential., Comment: 9 pages, including 9 figures and 3 tables, accepted for publication in MNRAS

Published
2010
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28. Present state and promises of the RAVE survey

Author

Steinmetz, M., Siebert, A., and Zwitter, T.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The RAdial Velocity Experiment (RAVE) is an ambitious survey to measure the radial velocities, temperatures, surface gravities, metallicities and abundance ratios for up to a million stars using the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO), over the period 2003 - 2011. The survey represents a big advance in our understanding of our own Milky Way galaxy. The main data product will be a southern hemisphere survey of about a million stars. Their selection is based exclusively on their I--band colour, so avoiding any colour-induced bias. RAVE is expected to be the largest spectroscopic survey of the Solar neighbourhood in the coming decade, but with a significant fraction of giant stars reaching out to 10 kpc from the Sun. RAVE offers the first truly representative inventory of stellar radial velocities for all major components of the Galaxy. Here we present the first scientific results of this survey as well as its second data release which doubles the number of previously released radial velocities. For the first time, the release also provides atmospheric parameters for a large fraction of the second year data, making it an unprecedented tool to study the formation of the Milky Way. Plans for further data releases are outlined., 8 pages, 5 Figures. To be published in the proceedings of the IAU Symp. 254, The Galaxy Disk in Cosmological Context, Copenhagen, June 9-13, 2008

Published
2008

29. Cosmic M��nage �� Trois: The Origin of Satellite Galaxies On Extreme Orbits

Author

Sales, L. V., Navarro, J. F., Abadi, M. G., and Steinmetz, M.

Subjects
Physics::Space Physics, Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We examine the orbits of satellite galaxies identified in a suite of N-body/gasdynamical simulations of the formation of $L_*$ galaxies in a LCDM universe. Most satellites follow conventional orbits; after turning around, they accrete into their host halo and settle on orbits whose apocentric radii are steadily eroded by dynamical friction. However, a number of outliers are also present, we find that ~1/3 of satellites identified at $z=0$ are on unorthodox orbits, with apocenters that exceed their turnaround radii. This population of satellites on extreme orbits consists typically of the faint member of a satellite pair that has been ejected onto a highly-energetic orbit during its first approach to the primary. Since the concurrent accretion of multiple satellite systems is a defining feature of hierarchical models of galaxy formation, we speculate that this three-body ejection mechanism may be the origin of (i) some of the newly discovered high-speed satellites around M31 (such as Andromeda XIV); (ii) some of the distant fast-receding Local Group members, such as Leo I; and (iii) the oddly isolated dwarf spheroidals Cetus and Tucana in the outskirts of the Local Group. Our results suggest that care must be exercised when using the orbits of the most weakly bound satellites to place constraints on the total mass of the Local Group., 10 pages, 6 figures, MNRAS in press. Accepted version with minor changes. Version with high resolution figures available at: http://www.astro.uvic.ca/~lsales/SatPapers/SatPapers.html

Published
2007
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30. OH and H2O maser variations in W33B

Author

Chiappini, C., Anders, F., Rodrigues, T., Miglio, A., Montalban, J., Mosser, B., Girardi, L., Valentini, M., Noels, A., Morel, T., Minchev, I., Steinmetz, M., Santiago, B., Schultheis, M., Martig, M., da Costa, L., Maia, M., Allende Prieto, C., de Assis Peralta, R., Hekker, S., Themessl, N., Kallinger, T., Garcia, R., Mathur, S., Baudin, F., Beers, T., Cunha, K., Harding, P., Holtzman, J., Majewski, S., Mészáros, Sz., Nidever, D., Pan, K., Schiavon, R., Shetrone, M., Schneider, D., Stassun, K., Colom, P., Lekht, E., Pashchenko, M., Rudnitskij, G., Leibniz-Institut für Astrophysik Potsdam (AIP), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), Département d'astrophysique, Géophysique et Océanographie (AGO), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Liverpool John Moores University (LJMU), Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), School of Physics and Astronomy, University of Birmingham [Birmingham], Institute for Astronomy [Vienna], University of Vienna [Vienna], Institut de Physique du Globe de Paris (IPG Paris), Space Science Institute [Boulder] (SSI), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Center for the Study of Cosmic Evolution (CSCE), Michigan State University [East Lansing], Michigan State University System-Michigan State University System, Department of Geography, Department of geography, Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris, Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
individual objects, 85A15, lines and bands -ISM, Astrophysics::High Energy Astrophysical Phenomena, Central object, FOS: Physical sciences, Astrophysics, 01 natural sciences, W33B, law.invention, Radio telescope, symbols.namesake, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Maser, masers -ISM, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, magnetic fields -ISM, Line (formation), [PHYS]Physics [physics], Physics, Zeeman effect, 010308 nuclear & particles physics, molecules -ISM, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Magnetic field, Wavelength, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), symbols, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Excitation
Abstract

The active star-forming region W33B is a source of OH and H2O maser emission located in distinct zones around the central object. The aim was to obtain the complete Stokes pattern of polarised OH maser emission, to trace its variability and to investigate flares and long-term variability of the H2O maser and evolution of individual emission features. Observations in the OH lines at a wavelength of 18 cm were carried out on the Nan\c{c}ay radio telescope (France) at a number of epochs in 2008--2014; H2O line observations (long-term monitoring) at a wavelength of 1.35 cm were performed on the 22-metre radio telescope of the Pushchino Radio Astronomy Observatory (Russia) between 1981 and 2014. We have observed strong variability of the emission features in the main 1665- and 1667-MHz OH lines as well as in the 1612-MHz satellite line. Zeeman splitting has been detected in the 1665-MHz OH line at 62 km/s and in the 1667-MHz line at 62 and 64 km/s. The magnetic field intensity was estimated to be from 2 to 3 mG. The H2O emission features form filaments, chains with radial-velocity gradients, or more complicated structures including large-scale ones. Long-term observations of the hydroxyl maser in the W33B region have revealed narrowband polarised emission in the 1612-MHz line with a double-peak profile characteristic of Type IIb circumstellar masers. The 30-year monitoring of the water-vapour maser in W33B showed several strong flares of the H2O line. The observed radial-velocity drift of the H2O emission features suggests propagation of an excitation wave in the masering medium with a gradient of radial velocities. In OH and H2O masers some turbulent motions of material are inferred., Comment: 18 pages, 12 figures

Published
2015

31. Pieces of the puzzle: ancient substructure in the Galactic disc

Author

Helmi, A., Navarro, J. F., Nordstrom, B., Holmberg, J., Abadi, M. G., Steinmetz, M., Kapteyn Astronomical Institute, and Astronomy

Subjects
SOLAR NEIGHBORHOOD, Y-2 ISOCHRONES, METAL-POOR STARS, solar neighbourhood, UVBY-BETA PHOTOMETRY, Galaxy : kinematics and dynamics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxy : disc, Galaxy : evolution, PROPER-MOTION STARS, COLD DARK-MATTER, STELLAR VELOCITY DISTRIBUTION, F-TYPE STARS, Astrophysics::Solar and Stellar Astrophysics, MILKY-WAY, Galaxies : evolution, Astrophysics::Earth and Planetary Astrophysics, GALAXY FORMATION, Galaxies : formation, Astrophysics::Galaxy Astrophysics
Abstract

We search for signatures of past accretion events in the Milky Way in the recently published catalogue by Nordstrom et al., containing accurate spatial and kinematic information as well as metallicities for 13 240 nearby stars. To optimize our strategy, we use numerical simulations and characterize the properties of the debris from disrupted satellites. We find that stars with a common progenitor should show distinct correlations between their orbital parameters; in particular, between the apocentre (A) and pericentre (P), as well as their z-angular momentum (L-z). In the APL space, such stars are expected to cluster around regions of roughly constant eccentricity. The APL space for the Nordstrom catalogue exhibits a wealth of substructure, much of which can be linked to dynamical perturbations induced by spiral arms and the Galactic bar. However, our analysis also reveals a statistically significant excess of stars on orbits of common ( moderate) eccentricity, analogous to the pattern expected for merger debris. Besides being dynamically peculiar, the 274 stars in these substructures have very distinct metallicity and age distributions, providing further evidence of their extragalactic provenance. It is possible to identify three coherent groups among these stars, that, in all likelihood, correspond to the remains of disrupted satellites. The most metal-rich group ([Fe/H] >= -0.45 dex) has 120 stars distributed into two stellar populations of similar to 8 Gyr (33 per cent) and similar to 12 Gyr (67 per cent) of age. The second group with similar to -0.6 dex has 86 stars and shows evidence of three populations of 8 Gyr ( 15 per cent), 12 Gyr (36 per cent) and 16 Gyr (49 per cent) of age. Finally, the third group has 68 stars, with typical metallicity around -0.8 dex and a single age of similar to 14 Gyr. The identification of substantial amounts of debris in the Galactic disc whose origin can be traced back to more than one satellite galaxy, provides evidence of the hierarchical formation of the Milky Way.

Published
2006

32. Pieces of the puzzle: Ancient substructure in the Galactic disk

Author

Helmi, Amina, Navarro, J. F., Nordstrom, B., Holmberg, J., Abadi, M. G., and Steinmetz, M.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We search for signatures of past accretion events in the Milky Way in the recently published catalogue by Nordstrom et al.(2004), containing accurate spatial and kinematic information as well as metallicities for 13240 nearby stars. To optimize our strategy, we use numerical simulations to characterize the properties of the debris from disrupted satellites. We find that stars with a common progenitor should show distinct correlations between their orbital parameters; in particular, between the apocentre A and pericentre P, as well as their z-angular momentum (L_z). In the APL-space, such stars are expected to cluster around regions of roughly constant eccentricity. The APL space for the Nordstrom catalogue exhibits a wealth of substructure, much of which can be linked to dynamical perturbations induced by spiral arms and the Galactic bar. However, our analysis also reveals a statistically significant excess of stars on orbits of common (moderate) eccentricity, analogous to the pattern expected for merger debris. Besides being dynamically peculiar, the 274 stars in these substructures have very distinct metallicity and age distributions, providing further evidence of their extra-Galactic provenance. It is possible to identify among these stars, three coherent Groups with characteristic ages and metallicities, that, in all likelihood, correspond to the remains of disrupted satellites. [abridged], 18 pages, 21 figures, MNRAS in press. Accepted version with high-resolution figures available from http://www.astro.rug.nl/~ahelmi/research/puzzle.html

Published
2005

33. The signature of substructure on gravitational lensing in the LCDM cosmological model

Author

Bradac, M., Schneider, P., Lombardi, M., Steinmetz, M., Koopmans, L. V. E., and Navarro, Julio F.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We present a study of the lens properties of quadruply imaged systems, lensed by numerically simulated galaxies. We investigate a simulated elliptical and disc galaxy drawn from high resolution simulations of galaxy formation in a concordance $\Lambda$CDM universe. The simulations include the effects of gas dynamics, star formation and feedback processes. Flux-ratio anomalies observed in strong gravitational lensing potentially provide an indicator for the presence of mass substructure in lens galaxies as predicted from CDM simulations. We particularly concentrate on the prediction that, for an ideal cusp caustic, the sum of the signed magnifications of the three highly magnified images should vanish when the source approaches the cusp. Strong violation of this cusp relation indicates the presence of substructure, regardless of the global, smooth mass model of the lens galaxy. We draw the following conclusions: (1) the level of substructure present in simulations produces violations of the cusp relation comparable to those observed, (2) higher-order catastrophes (e.g. swallowtails) can also cause changes of the order of 0.6 in the cusp relation as predicted by a smooth model, (3) the flux anomaly distribution depends on the image parity and flux and both the brightest minimum and saddle-point images are more affected by substructure than the fainter images. In addition, the brightest saddle point is demagnified w.r.t. the brightest minimum. Our results are fully numerical and properly include all mass scales, without making semi-analytic assumptions. They are ultimately limited by the mass resolution of single particles in the simulation determined by current computational limits, however show that our results are not affected by shot-noise due to the finite number of particles., Comment: 14 pages,9 figures, Accepted for publication in A&A. High resolution colour and B&W versions of this paper are available at http://www.astro.uni-bonn.de/~mbradac/Work/index.html

Published
2003
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34. Using VLBI Data to Investigate the Galaxy Structure in the Gravitationally Lensed System B1422+231

Author

Bradač, M., Schneider, P., Steinmetz, M., MARCO LOMBARDI, King, L. J., and Porcas, R. W.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Gravitationally lensed systems with multiply imaged quasars are an excellent tool for studying the properties of distant galaxies. In particular, they provide the most accurate mass measures for the lensing galaxy. The system B1422+231 is a well studied example of a quadruply imaged quasar, with high-quality VLBI data available. Very accurate data on image positions, fluxes and deconvolved image sizes provide good constraints for lensing models. We discuss here the failure of smooth models in fitting the data. Since it is intuitively clear that the mass of a lens galaxy is not a smooth entity, we have investigated how deviation from a smooth model can influence lensing phenomena, especially the image flux ratios. To explore expectations about the level of substructure in galaxies and its influence on strong lensing, N-body simulations of a model galaxy are employed. By using the mass distribution of this model galaxy as a lens, synthetic data sets of different four image system configurations are generated. Their analysis can possibly provide evidence for the presence and strong influence of substructure in the primary lens galaxy., to appear in proceedings of the 6th European VLBI Network Symposium, MPIfR, Bonn, Germany (2002)

Published
2002

35. The Gaia-ESO Public Spectroscopic Survey

Author

Gilmore, G., Randich, S., Asplund, M., Binney, J., Bonifacio, P., Drew, J., Feltzing, S., Ferguson, A., Jeffries, R., Micela, G., Negueruela, I., Prusti, T., Rix, H. -W, Vallenari, A., Alfaro, E., Allende-Prieto, C., Babusiaux, C., Bensby, T., Blomme, R., Bragaglia, A., Flaccomio, E., François, P., Irwin, M., Koposov, S., Korn, A., Lanzafame, A., Pancino, E., Paunzen, E., Recio-Blanco, A., Sacco, G., Smiljanic, R., Eck, S., Walton, N., Aden, D., Aerts, C., Affer, L., Alcala, J. -M, Altavilla, G., Alves, J., Antoja, T., Arenou, F., Costanza ARGIROFFI, Asensio Ramos, A., Bailer-Jones, C., Balaguer-Nunez, L., Bayo, A., Barbuy, B., Barisevicius, G., Barrado Y Navascues, D., Battistini, C., Bellas Velidis, I., Bellazzini, M., Belokurov, V., Bergemann, M., Bertelli, G., Biazzo, K., Bienayme, O., Bland-Hawthorn, J., Boeche, C., Bonito, S., Boudreault, S., Bouvier, J., Brandao, I., Brown, A., Bruijne, J., Burleigh, M., Caballero, J., Caffau, E., Calura, F., Capuzzo-Dolcetta, R., Caramazza, M., Carraro, G., Casagrande, L., Casewell, S., Chapman, S., Chiappini, C., Chorniy, Y., Christlieb, N., Cignoni, M., Cocozza, G., Colless, M., Collet, R., Collins, M., Correnti, M., Covino, E., Crnojevic, D., Cropper, M., Cunha, M., Damiani, F., David, M., Delgado, A., Duffau, S., Edvardsson, B., Eldridge, J., Enke, H., Eriksson, K., Evans, N. W., Eyer, L., Famaey, B., Fellhauer, M., Ferreras, I., Figueras, F., Fiorentino, G., Flynn, C., Folha, D., Franciosini, E., Frasca, A., Freeman, K., Fremat, Y., Friel, E., Gaensicke, B., Gameiro, J., Garzon, F., Geier, S., Geisler, D., Gerhard, O., Gibson, B., Gomboc, A., Gomez, A., Gonzalez-Fernandez, C., Gonzalez Hernandez, J., Gosset, E., Grebel, E., Greimel, R., Groenewegen, M., Grundahl, F., Guarcello, M., Gustafsson, B., Hadrava, P., Hatzidimitriou, D., Hambly, N., Hammersley, P., Hansen, C., Haywood, M., Heber, U., Heiter, U., Held, E., Helmi, A., Hensler, G., Herrero, A., Hill, V., Hodgkin, S., Huelamo, N., Huxor, A., Ibata, R., Jackson, R., Jong, R., Jonker, P., Jordan, S., Jordi, C., Jorissen, A., Katz, D., Kawata, D., Keller, S., Kharchenko, N., Klement, R., Klutsch, A., Knude, J., Koch, A., Kochukhov, O., Kontizas, M., Koubsky, P., Lallement, R., Laverny, P., Leeuwen, F., Lemasle, B., Lewis, G., Lind, K., Lindstrom, H. P. E., Lobel, A., Lopez Santiago, J., Lucas, P., Ludwig, H., Lueftinger, T., Magrini, L., Maiz Apellaniz, J., Maldonado, J., Marconi, G., Marino, A., Martayan, C., Martinez-Valpuesta, I., Matijevic, G., Mcmahon, R., Messina, S., Meyer, M., Miglio, A., Mikolaitis, S., Minchev, I., Minniti, D., Moitinho, A., Momany, Y., Monaco, L., Montalto, M., Monteiro, M. J., Monier, R., Montes, D., Mora, A., Moraux, E., Morel, T., Mowlavi, N., Mucciarelli, A., Munari, U., Napiwotzki, R., Nardetto, N., Naylor, T., Naze, Y., Nelemans, G., Okamoto, S., Ortolani, S., Pace, G., Palla, F., Palous, J., Parker, R., Penarrubia, J., Pillitteri, I., Piotto, G., Posbic, H., Prisinzano, L., Puzeras, E., Quirrenbach, A., Ragaini, S., Read, J., Read, M., Reyle, C., Ridder, J., Robichon, N., Robin, A., Roeser, S., Romano, D., Royer, F., Ruchti, G., Ruzicka, A., Ryan, S., Ryde, N., Santos, N., Sanz Forcada, J., Sarro Baro, L. M., Sbordone, L., Schilbach, E., Schmeja, S., Schnurr, O., Schoenrich, R., Scholz, R. -D, Seabroke, G., Sharma, S., Silva, G., Smith, M., Solano, E., Sordo, R., Soubiran, C., Sousa, S., Spagna, A., Steffen, M., Steinmetz, M., Stelzer, B., Stempels, E., Tabernero, H., Tautvaisiene, G., Thevenin, F., Torra, J., Tosi, M., Tolstoy, E., Turon, C., Walker, M., Wambsganss, J., Worley, C., Venn, K., Vink, J., Wyse, R., Zaggia, S., Zeilinger, W., Zoccali, M., Zorec, J., Zucker, D., Zwitter, T., Gaia-ESO Survey Team, Gilmore, G., Randich, S., Asplund, M., Binney, J., Bonifacio, P., Drew, J., Feltzing, S., Ferguson, A., Jeffries, R., Micela, G., Negueruela, I., Prusti, T., Rix, H.-W., Vallenari, A., Alfaro, E., Allende-Prieto, C., Babusiaux, C., Bensby, T., Blomme, R., Bragaglia, A., Flaccomio, E., François, P., Irwin, M., Koposov, S., Korn, A., Lanzafame, A., Pancino, E., Paunzen, E., Recio-Blanco, A., Sacco, G., Smiljanic, R., Van Eck, S., Walton, N., Aden, D., Aerts, C., Affer, L., Alcala, J.-M., Altavilla, G., Alves, J., Antoja, T., Arenou, F., Argiroffi, C., Asensio Ramos, A., Bailer-Jones, C., Balaguer-Nunez, L., Bayo, A., Barbuy, B., Barisevicius, G., Barrado y Navascues, D., Battistini, C., Bellas Velidis, I., Bellazzini, M., Belokurov, V., Bergemann, M., Bertelli, G., Biazzo, K., Bienayme, O., Bland-Hawthorn, J., Boeche, C., Bonito, S., Boudreault, S., Bouvier, J., Brandao, I., Brown, A., de Bruijne, J., Burleigh, M., Caballero, J., Caffau, E., Calura, F., Capuzzo-Dolcetta, R., Caramazza, M., Carraro, G., Casagrande, L., Casewell, S., Chapman, S., Chiappini, C., Chorniy, Y., Christlieb, N., Cignoni, M., Cocozza, G., Colless, M., Collet, R., Collins, M., Correnti, M., Covino, E., Crnojevic, D., Cropper, M., Cunha, M., Damiani, F., David, M., Delgado, A., Duffau, S., Edvardsson, B., Eldridge, J., Enke, H., Eriksson, K., Evans, N. W., Eyer, L., Famaey, B., Fellhauer, M., Ferreras, I., Figueras, F., Fiorentino, G., Flynn, C., Folha, D., Franciosini, E., Frasca, A., Freeman, K., Fremat, Y., Friel, E., Gaensicke, B., Gameiro, J., Garzon, F., Geier, S., Geisler, D., Gerhard, O., Gibson, B., Gomboc, A., Gomez, A., Gonzalez-Fernandez, C., Gonzalez Hernandez, J., Gosset, E., Grebel, E., Greimel, R., Groenewegen, M., Grundahl, F., Guarcello, M., Gustafsson, B., Hadrava, P., Hatzidimitriou, D., Hambly, N., Hammersley, P., Hansen, C., Haywood, M., Heber, U., Heiter, U., Held, E., Helmi, A., Hensler, G., Herrero, A., Hill, V., Hodgkin, S., Huelamo, N., Huxor, A., Ibata, R., Jackson, R., de Jong, R., Jonker, P., Jordan, S., Jordi, C., Jorissen, A., Katz, D., Kawata, D., Keller, S., Kharchenko, N., Klement, R., Klutsch, A., Knude, J., Koch, A., Kochukhov, O., Kontizas, M., Koubsky, P., Lallement, R., de Laverny, P., van Leeuwen, F., Lemasle, B., Lewis, G., Lind, K., Lindstrom, H. P. E., Lobel, A., Lopez Santiago, J., Lucas, P., Ludwig, H., Lueftinger, T., Magrini, L., Maiz Apellaniz, J., Maldonado, J., Marconi, G., Marino, A., Martayan, C., Martinez-Valpuesta, I., Matijevic, G., McMahon, R., Messina, S., Meyer, M., Miglio, A., Mikolaitis, S., Minchev, I., Minniti, D., Moitinho, A., Momany, Y., Monaco, L., Montalto, M., Monteiro, M. J., Monier, R., Montes, D., Mora, A., Moraux, E., Morel, T., Mowlavi, N., Mucciarelli, A., Munari, U., Napiwotzki, R., Nardetto, N., Naylor, T., Naze, Y., Nelemans, G., Okamoto, S., Ortolani, S., Pace, G., Palla, F., Palous, J., Parker, R., Penarrubia, J., Pillitteri, I., Piotto, G., Posbic, H., Prisinzano, L., Puzeras, E., Quirrenbach, A., Ragaini, S., Read, J., Read, M., Reyle, C., De Ridder, J., Robichon, N., Robin, A., Roeser, S., Romano, D., Royer, F., Ruchti, G., Ruzicka, A., Ryan, S., Ryde, N., Santos, N., Sanz Forcada, J., Sarro Baro, L. M., Sbordone, L., Schilbach, E., Schmeja, S., Schnurr, O., Schoenrich, R., Scholz, R.-D., Seabroke, G., Sharma, S., De Silva, G., Smith, M., Solano, E., Sordo, R., Soubiran, C., Sousa, S., Spagna, A., Steffen, M., Steinmetz, M., Stelzer, B., Stempels, E., Tabernero, H., Tautvaisiene, G., Thevenin, F., Torra, J., Tosi, M., Tolstoy, E., Turon, C., Walker, M., Wambsganss, J., Worley, C., Venn, K., Vink, J., Wyse, R., Zaggia, S., Zeilinger, W., Zoccali, M., Zorec, J., Zucker, D., and Zwitter, T.

Subjects
spectroscopy, stars, kinematics, abundances, Settore FIS/05 - Astronomia E Astrofisica, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The Gaia-ESO Public Spectroscopic Survey has begun and will obtain high quality spectroscopy of some 100000 Milky Way stars, in the field and in open clusters, down to magnitude 19, systematically covering all the major components of the Milky Way. This survey will provide the first homogeneous overview of the distributions of kinematics and chemical element abundances in the Galaxy. The motivation, organisation and implementation of the Gaia-ESO Survey are described, emphasising the complementarity with the ESA Gaia mission. Spectra from the very first observing run of the survey are presented.

36. VizieR Online Data Catalog: RAVE 3rd data release (Siebert+, 2011)

Author

Siebert, A., Williams, M., Siviero, A., Reid, W., Boeche, C., Steinmetz, M., Fulbright, J., Munari, U., Zwitter, T., Watson, F. G., Wyse, R. F. G., de Jong, R. S., Enke, H., Anguiano, B., Burton, D., Cass, C. J. P., Fiegert, K., Hartley, M., Ritter, A., Russel, K. S., Stupar, M., Bienayme, O., Freeman, K. C., Gilmore, G., Grebel, E. K., Helmi, A., Navarro, J. F., Binney, J., Bland-Hawthorn, J., Campbell, R., Famaey, B., Gerhard, O., Gibson, B. K., Matijevic, G., Parker, Q. A., Seabroke, G. M., Sharma, S., Smith, M. C., Wylie-de Boer, E., and Kapteyn Astronomical Institute

Subjects
Milky Way, Photometry, Radial velocities, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Surveys, Stars: fundamental, Astrophysics::Galaxy Astrophysics
Abstract

Spectroscopic radial velocities for 83,072 stars in the Milky-Way southern hemisphere using the 6dF instrument at the AAO. Stellar parameters are published for a set of 39,833 stars belonging to the second and third years of observation. (1 data file).

37. RAVE DR2 distance catalogue (Breddels+, 2010)

Author

Breddels, M. A., Smith, M. C., Helmi, A., Bienayme, O., Binney, J., Bland-Hawthorn, J., Boeche, C., Burnett, B. C. M., Campbell, R., Freeman, K. C., Gibson, B., Gilmore, G., Grebel, E. K., Munari, U., Navarro, J. F., Parker, Q. A., Seabroke, G. M., Siebert, A., Siviero, A., Steinmetz, M., Watson, F. G., Williams, M., Wyse, R. F. G., Zwitter, T., and Astronomy

Subjects
Milky Way, Radial velocities, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Surveys, Stars: distances, Astrophysics::Galaxy Astrophysics
Abstract

We used stellar models combined with atmospheric properties from RAVE (effective temperature, surface gravity and metallicity) and (J-Ks) photometry from archival sources to derive absolute magnitudes. In combination with apparent magnitudes, sky coordinates, proper motions from a variety of sources and radial velocities from RAVE, we are able

38. RAVE 3rd data release (Siebert+, 2011)

Author

Siebert, A., Williams, M., Siviero, A., Reid, W., Boeche, C., Steinmetz, M., Fulbright, J., Munari, U., Zwitter, T., Watson, F. G., Wyse, R. F. G., de Jong, R.S., Enke, H., Anguiano, B., Burton, D., Cass, C. J. P., Fiegert, K., Hartley, M., Ritter, A., Russel, K. S., Stupar, M., Bienayme, O., Freeman, K. C., Gilmore, G., Grebel, E. K., Helmi, A., Navarro, J. F., Binney, J., Bland-Hawthorn, J., Campbell, R., Famaey, B., Gerhard, O., Gibson, B. K., Matijevic, G., Parker, Q. A., Seabroke, G. M., Sharma, S., Smith, M. C., Wylie-de Boer, E., and Astronomy

Subjects
Milky Way, Photometry, Radial velocities, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Surveys, Stars: fundamental, Astrophysics::Galaxy Astrophysics
Abstract

Spectroscopic radial velocities for 83,072 stars in the Milky-Way southern hemisphere using the 6dF instrument at the AAO. Stellar parameters are published for a set of 39,833 stars belonging to the second and third years of observation.

39. Very metal-poor stars observed by the RAVE survey

Author

Matijevic, G, Chiappini, C, Grebel, EK, Wyse, RFG, Zwitter, T, Bienayme, O, Bland-Hawthorn, J, Freeman, KC, Gibson, BK, Gilmore, G, Helmi, A, Kordopatis, G, Kunder, A, Munari, U, Navarro, JF, Parker, QA, Reid, W, Seabroke, G, Siviero, A, Steinmetz, M, and Watson, F

Subjects
stars: abundances, Galaxy: abundances, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, methods: data analysis, Astrophysics::Galaxy Astrophysics
Abstract

Metal-poor stars trace the earliest phases in the chemical enrichment of the Universe. They give clues about the early assembly of the Galaxy as well as on the nature of the first stellar generations. Multi-object spectroscopic surveys play a key role in finding these fossil records in large volumes. Here we present a novel analysis of the metal-poor star sample in the complete Radial Velocity Experiment (RAVE) Data Release 5 catalog with the goal of identifying and characterizing all very metal-poor stars observed by the survey. Using a three-stage method, we first identified the candidate stars using only their spectra as input information. We employed an algorithm called t-SNE to construct a low-dimensional projection of the spectrum space and isolate the region containing metal-poor stars. Following this step, we measured the equivalent widths of the near-infrared Ca ii triplet lines with a method based on flexible Gaussian processes to model the correlated noise present in the spectra. In the last step, we constructed a calibration relation that converts the measured equivalent widths and the color information coming from the 2MASS and WISE surveys into metallicity and temperature estimates. We identified 877 stars with at least a 50% probability of being very metal-poor ([Fe=H] < 2 dex), out of which 43 are likely extremely metal-poor ([Fe=H] < 3 dex). The comparison of the derived values to a small subsample of stars with literature metallicity values shows that our method works reliably and correctly estimates the uncertainties, which typically have values [Fe=H] 0:2 dex. In addition, when compared to the metallicity results derived using the RAVE DR5 pipeline, it is evident that we achieve better accuracy than the pipeline and therefore more reliably evaluate the very metal-poor subsample. Based on the repeated observations of the same stars, our method gives very consistent results. We intend to study the identified sample further by acquiring high-resolution spectroscopic follow-up observations. The method used in this work can also easily be extended to other large-scale data sets, including to the data from the Gaia mission and the upcoming 4MOST survey.

40. The eROSITA X-ray telescope on SRG

Author

Robert Andritschke, Christian Schmid, Joern Wilms, T. Mernik, Josef Eder, C. Tenzer, Mara Salvato, Lothar Strüder, Lars Tiedemann, Michael Freyberg, V. Arefiev, E. Churazov, V. Babyshkin, Esra Bulbul, Benjamin Mican, H. Scheuerle, Axel Schwope, Hermann Brunner, D. Coutinho, Georg Lamer, Jan Robrade, Miriam E. Ramos-Ceja, Heinrich Bräuninger, Elmar Pfeffermann, Kirpal Nandra, Peter Friedrich, Marcella Brusa, Tanja Eraerds, Joachim Trümper, I. Lomakin, I. Lapshov, Antonis Georgakakis, Joseph J. Mohr, W. Kink, A. Gueguen, Thomas H. Reiprich, Vadim Burwitz, Daniel Pietschner, Frank Haberl, N. Clerc, Jonas Reiffers, Ian M. Stewart, O. Batanov, Chandreyee Maitra, Katharina Borm, M. Buntov, V. Nazarov, Th. Boller, Alexis Finoguenov, Sebastian Müller, Emanuele Perinati, Matthias Steinmetz, A. Shirshakov, S. Friedrich, Valeri Yaroshenko, F. Korotkov, Peter Predehl, Andreas von Kienlin, P. Weber, Valentin Emberger, M. N. Pavlinsky, Florian Pacaud, W. Bornemann, Thomas Dauser, Marcus Brüggen, Norbert Meidinger, Gisela Hartner, Konrad Dennerl, A. V. Bogomolov, O. Hälker, P. Gureev, B. Menz, Wolfgang Burkert, Jeremy S. Sanders, Werner Becker, Andrea Merloni, Rashid Sunyaev, Long Ji, V. Voron, S. Granato, Maria Fürmetz, Manami Sasaki, Andrea Santangelo, Hans Böhringer, Guenther Hasinger, Arne Rau, Victor Doroshenko, H. Huber, Ingo Kreykenbohm, Tie Liu, Marat Gilfanov, Christoph Grossberger, Jürgen H. M. M. Schmitt, Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Max-Planck-Institut für Extraterrestrische Physik (MPE), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Predehl P., Andritschke R., Arefiev V., Babyshkin V., Batanov O., Becker W., Boehringer H., Bogomolov A., Boller T., Borm K., Bornemann W., Br'auninger H., Br'uggen M., Brunner H., Brusa M., Bulbul E., Buntov M., Burwitz V., Burkert W., Clerc N., Churazov E., Coutinho D., Dauser T., Dennerl K., Doroshenko V., Eder J., Emberger V., Eraerds T., Finoguenov A., Freyberg M., Friedrich P., Friedrich S., Fuermetz M., Georgakakis A., Gilfanov M., Granato S., Grossberger C., Gueguen A., Gureev P., Haberl F., Haelker O., Hartner G., Hasinger G., Huber H., Ji L., Kienlin A., v., Kink W., Korotkov F., Kreykenbohm I., Lamer G., Lomakin I., Lapshov I., Liu T., Maitra C., Meidinger N., Menz B., Merloni A., Mernik T., Mican B., Mohr J., M'uller S., Nandra K., Nazarov V., Pacaud F., Pavlinsky M., Perinati E., Pfeffermann E., Pietschner D., Ramos-Ceja M.,~E., Rau A., Reiffers J., Reiprich T.,~H., Robrade J., Salvato M., Sanders J., Santangelo A., Sasaki M., Scheuerle H., Schmid C., Schmitt J., Schwope A., Shirshakov A., Steinmetz M., Stewart I., Strueder L., Sunyaev R., Tenzer C., Tiedemann L., Truemper J., Voron V., Weber P., Wilms J., Yaroshenko V., Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
X-rays general, media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, X-ray telescope, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Surveys, 01 natural sciences, 7. Clean energy, law.invention, Telescope, space vehicles: instruments, X-rays: general, surveys, dark energy, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, law, 0103 physical sciences, ROSAT, Dark energy, Space vehicles instruments, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Supermassive black hole, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Celestial sphere, Galaxy, Redshift, Space and Planetary Science, Sky, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2--2.3\,keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3--8\,keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts $z>1$ in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements., 16 pages, 19 figures, accepted by Astronomy & Astrophysics

Published
2021

41. The Sixth Data Release of the Radial Velocity Experiment (R ave). II. Stellar Atmospheric Parameters, Chemical Abundances, and Distances

Author

Savita Mathur, Quentin A. Parker, Diego Bossini, I. Carrillo, Amina Helmi, Cristina Chiappini, Luca Casagrande, Marica Valentini, Paul J. McMillan, Teresa Antoja, Brad K. Gibson, Sanjib Sharma, Kenneth C. Freeman, Benoit Famaey, Andrea Miglio, Harry Enke, Joss Bland-Hawthorn, Rosemary F. G. Wyse, G. R. Ruchti, Georges Kordopatis, George M. Seabroke, Benoit Mosser, Gal Matijevic, Julio F. Navarro, M. Stupar, Fred Watson, Alessandro Siviero, Mary E K Williams, J. P. Fulbright, Gerard Gilmore, Kseniia Sysoliatina, Giacomo Monari, Tomaž Zwitter, Paul Cass, Danijela Birko, Friedrich Anders, Yvonne Elsworth, Eva K. Grebel, Warren A. Reid, Ulisse Munari, Kristin Fiegert, Olivier Bienaymé, Andreas Ritter, Alejandra Recio-Blanco, James Binney, Thaíse S. Rodrigues, Guillaume Guiglion, Arnaud Siebert, Ralf-Dieter Scholz, Patrick de Laverny, Paula Jofre, Andreas Just, D. Burton, Ortwin Gerhard, Jennifer Wojno, Ivan Minchev, William J. Chaplin, Albert Bijaoui, Andrea Kunder, Borja Anguiano, Rafael A. García, Matthias Steinmetz, Leibniz Institute for Astrophysics Potsdam, Australian Astronomical Observatory, Australian National University, Australian Research Council, Agence Nationale de la Recherche (France), German Research Foundation, European Research Council, Istituto Nazionale di Astrofisica, Johns Hopkins University, National Science Foundation (US), W. M. Keck Foundation, Macquarie University, Netherlands Research School for Astronomy, Natural Sciences and Engineering Research Council of Canada, Slovenian Research Agency, Swiss National Science Foundation, Science and Technology Facilities Council (UK), Opticon, Observatoire Astronomique de Strasbourg, University of Basel, University of Groningen, University of Heidelberg, University of Sydney, Centre National D'Etudes Spatiales (France), Ministerio de Economía y Competitividad (España), Kavli Institute for Theoretical Physics, Simons Foundation, Steinmetz M., Guiglion G., McMillan P.J., Matijevic G., Enke H., Kordopatis G., Zwitter T., Valentini M., Chiappini C., Casagrande L., Wojno J., Anguiano B., Bienayme O., Bijaoui A., Binney J., Burton D., Cass P., De Laverny P., Fiegert K., Freeman K., Fulbright J.P., Gibson B.K., Gilmore G., Grebel E.K., Helmi A., Kunder A., Munari U., Navarro J.F., Parker Q., Ruchti G.R., Recio-Blanco A., Reid W., Seabroke G.M., Siviero A., Siebert A., Stupar M., Watson F., Williams M.E.K., Wyse R.F.G., Anders F., Antoja T., Birko D., Bland-Hawthorn J., Bossini D., Garcia R.A., Carrillo I., Chaplin W.J., Elsworth Y., Famaey B., Gerhard O., Jofre P., Just A., Mathur S., Miglio A., Minchev I., Monari G., Mosser B., Ritter A., Rodrigues T.S., Scholz R.-D., Sharma S., Sysoliatina K., Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Astronomy

Subjects
010504 meteorology & atmospheric sciences, ACCURACY, FOS: Physical sciences, Library science, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, surveys, Observatory, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, KINEMATICS, Abundances, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, F-DWARF, European research, Surveys - Stars, Astronomy and Astrophysics, DISC, Astrophysics - Astrophysics of Galaxies, Distances, Astrophysics - Solar and Stellar Astrophysics, stars: abundances - distances, 13. Climate action, Space and Planetary Science, Research council, Astrophysics of Galaxies (astro-ph.GA), PATTERN SPEED, MILKY, Christian ministry, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics::Earth and Planetary Astrophysics, EXPERIMENT RAVE, SKY SURVEY, Data release, STARS, ISOCHRONES
Abstract

We present part 2 of the sixth and final Data Release (DR6) of the Radial Velocity Experiment (Rave), a magnitude-limited spectroscopic survey of Galactic stars randomly selected in Earth's southern hemisphere. The Rave medium-resolution spectra (R ∼ 7500) cover the Ca triplet region (8410-8795 Å) and span the complete time frame from the start of Rave observations on 2003 April 12 to their completion on 2013 April 4. In the second of two publications, we present the data products derived from 518,387 observations of 451,783 unique stars using a suite of advanced reduction pipelines focusing on stellar atmospheric parameters, in particular purely spectroscopically derived stellar atmospheric parameters, and the overall metallicity), enhanced stellar atmospheric parameters inferred via a Bayesian pipeline using Gaia DR2 astrometric priors, and asteroseismically calibrated stellar atmospheric parameters for giant stars based on asteroseismic observations for 699 K2 stars. In addition, we provide abundances of the elements Fe, Al, and Ni, as well as an overall [α/Fe] ratio obtained using a new pipeline based on the GAUGUIN optimization method that is able to deal with variable signal-to-noise ratios. The Rave DR6 catalogs are cross-matched with relevant astrometric and photometric catalogs, and are complemented by orbital parameters and effective temperatures based on the infrared flux method. The data can be accessed via the Rave website (http://rave-survey.org) or the Vizier database., Funding for Rave has been provided by: the Leibniz-Institut f¨ur Astrophysik Potsdam (AIP); the Australian Astronomical Observatory; the Australian National University; the Australian Research Council; the French National Research Agency (Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU with INP and IN2P3, co-funded by CEA and CNES); the German Research Foundation (SPP 1177 and SFB 881); the European Research Council (ERC-StG 240271 Galactica); the Istituto Nazionale di Astrofisica at Padova; The Johns Hopkins University; the National Science Foundation of the USA (AST-0908326); the W. M. Keck foundation; the Macquarie University; the Netherlands Research School for Astronomy; the Natural Sciences and Engineering Research Council of Canada; the Slovenian Research Agency (research core funding no. P1-0188); the Swiss National Science Foundation; the Science & Technology Facilities Council of the UK; Opticon; Strasbourg Observatory; and the Universities of Basel, Groningen, Heidelberg, and Sydney. PJM is supported by grant 2017-03721 from the Swedish Research Council. LC is the recipient of the ARC Future Fellowship FT160100402. RAG acknowledges the support from the PLATO CNES grant. SM would like to acknowledge support from the Spanish Ministry with the Ramon y Cajal fellowship number RYC-2015-17697. MS thanks the Research School of Astronomy & Astrophysics in Canberra for support through a Distinguished Visitor Fellowship. RFGW thanks the Kavli Institute for Theoretical Physics and the Simons Foundation for support as a Simons Distinguished Visiting Scholar. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958 to KITP.

Published
2020

42. The 16th Data Release of the Sloan Digital Sky Surveys : First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra

Author

Romina Ahumada, Carlos Allende Prieto, Andrés Almeida, Friedrich Anders, Scott F. Anderson, Brett H. Andrews, Borja Anguiano, Riccardo Arcodia, Eric Armengaud, Marie Aubert, Santiago Avila, Vladimir Avila-Reese, Carles Badenes, Christophe Balland, Kat Barger, Jorge K. Barrera-Ballesteros, Sarbani Basu, Julian Bautista, Rachael L. Beaton, Timothy C. Beers, B. Izamar T. Benavides, Chad F. Bender, Mariangela Bernardi, Matthew Bershady, Florian Beutler, Christian Moni Bidin, Jonathan Bird, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton, Médéric Boquien, Jura Borissova, Jo Bovy, W. N. Brandt, Jonathan Brinkmann, Joel R. Brownstein, Kevin Bundy, Martin Bureau, Adam Burgasser, Etienne Burtin, Mariana Cano-Díaz, Raffaella Capasso, Michele Cappellari, Ricardo Carrera, Solène Chabanier, William Chaplin, Michael Chapman, Brian Cherinka, Cristina Chiappini, Peter Doohyun Choi, S. Drew Chojnowski, Haeun Chung, Nicolas Clerc, Damien Coffey, Julia M. Comerford, Johan Comparat, Luiz da Costa, Marie-Claude Cousinou, Kevin Covey, Jeffrey D. Crane, Katia Cunha, Gabriele da Silva Ilha, Yu Sophia Dai, Sanna B. Damsted, Jeremy Darling, James W. Davidson, Roger Davies, Kyle Dawson, Nikhil De, Axel de la Macorra, Nathan De Lee, Anna Bárbara de Andrade Queiroz, Alice Deconto Machado, Sylvain de la Torre, Flavia Dell’Agli, Hélion du Mas des Bourboux, Aleksandar M. Diamond-Stanic, Sean Dillon, John Donor, Niv Drory, Chris Duckworth, Tom Dwelly, Garrett Ebelke, Sarah Eftekharzadeh, Arthur Davis Eigenbrot, Yvonne P. Elsworth, Mike Eracleous, Ghazaleh Erfanianfar, Stephanie Escoffier, Xiaohui Fan, Emily Farr, José G. Fernández-Trincado, Diane Feuillet, Alexis Finoguenov, Patricia Fofie, Amelia Fraser-McKelvie, Peter M. Frinchaboy, Sebastien Fromenteau, Hai Fu, Lluís Galbany, Rafael A. Garcia, D. A. García-Hernández, Luis Alberto Garma Oehmichen, Junqiang Ge, Marcio Antonio Geimba Maia, Doug Geisler, Joseph Gelfand, Julian Goddy, Violeta Gonzalez-Perez, Kathleen Grabowski, Paul Green, Catherine J. Grier, Hong Guo, Julien Guy, Paul Harding, Sten Hasselquist, Adam James Hawken, Christian R. Hayes, Fred Hearty, S. Hekker, David W. Hogg, Jon A. Holtzman, Danny Horta, Jiamin Hou, Bau-Ching Hsieh, Daniel Huber, Jason A. S. Hunt, J. Ider Chitham, Julie Imig, Mariana Jaber, Camilo Eduardo Jimenez Angel, Jennifer A. Johnson, Amy M. Jones, Henrik Jönsson, Eric Jullo, Yerim Kim, Karen Kinemuchi, Charles C. Kirkpatrick IV, George W. Kite, Mark Klaene, Jean-Paul Kneib, Juna A. Kollmeier, Hui Kong, Marina Kounkel, Dhanesh Krishnarao, Ivan Lacerna, Ting-Wen Lan, Richard R. Lane, David R. Law, Jean-Marc Le Goff, Henry W. Leung, Hannah Lewis, Cheng Li, Jianhui Lian, Lihwai Lin, Dan Long, Penélope Longa-Peña, Britt Lundgren, Brad W. Lyke, J. Ted Mackereth, Chelsea L. MacLeod, Steven R. Majewski, Arturo Manchado, Claudia Maraston, Paul Martini, Thomas Masseron, Karen L. Masters, Savita Mathur, Richard M. McDermid, Andrea Merloni, Michael Merrifield, Szabolcs Mészáros, Andrea Miglio, Dante Minniti, Rebecca Minsley, Takamitsu Miyaji, Faizan Gohar Mohammad, Benoit Mosser, Eva-Maria Mueller, Demitri Muna, Andrea Muñoz-Gutiérrez, Adam D. Myers, Seshadri Nadathur, Preethi Nair, Kirpal Nandra, Janaina Correa do Nascimento, Rebecca Jean Nevin, Jeffrey A. Newman, David L. Nidever, Christian Nitschelm, Pasquier Noterdaeme, Julia E. O’Connell, Matthew D. Olmstead, Daniel Oravetz, Audrey Oravetz, Yeisson Osorio, Zachary J. Pace, Nelson Padilla, Nathalie Palanque-Delabrouille, Pedro A. Palicio, Hsi-An Pan, Kaike Pan, James Parker, Romain Paviot, Sebastien Peirani, Karla Peña Ramŕez, Samantha Penny, Will J. Percival, Ismael Perez-Fournon, Ignasi Pérez-Ràfols, Patrick Petitjean, Matthew M. Pieri, Marc Pinsonneault, Vijith Jacob Poovelil, Joshua Tyler Povick, Abhishek Prakash, Adrian M. Price-Whelan, M. Jordan Raddick, Anand Raichoor, Amy Ray, Sandro Barboza Rembold, Mehdi Rezaie, Rogemar A. Riffel, Rogério Riffel, Hans-Walter Rix, Annie C. Robin, A. Roman-Lopes, Carlos Román-Zúñiga, Benjamin Rose, Ashley J. Ross, Graziano Rossi, Kate Rowlands, Kate H. R. Rubin, Mara Salvato, Ariel G. Sánchez, Laura Sánchez-Menguiano, José R. Sánchez-Gallego, Conor Sayres, Adam Schaefer, Ricardo P. Schiavon, Jaderson S. Schimoia, Edward Schlafly, David Schlegel, Donald P. Schneider, Mathias Schultheis, Axel Schwope, Hee-Jong Seo, Aldo Serenelli, Arman Shafieloo, Shoaib Jamal Shamsi, Zhengyi Shao, Shiyin Shen, Matthew Shetrone, Raphael Shirley, Víctor Silva Aguirre, Joshua D. Simon, M. F. Skrutskie, Anže Slosar, Rebecca Smethurst, Jennifer Sobeck, Bernardo Cervantes Sodi, Diogo Souto, David V. Stark, Keivan G. Stassun, Matthias Steinmetz, Dennis Stello, Julianna Stermer, Thaisa Storchi-Bergmann, Alina Streblyanska, Guy S. Stringfellow, Amelia Stutz, Genaro Suárez, Jing Sun, Manuchehr Taghizadeh-Popp, Michael S. Talbot, Jamie Tayar, Aniruddha R. Thakar, Riley Theriault, Daniel Thomas, Zak C. Thomas, Jeremy Tinker, Rita Tojeiro, Hector Hernandez Toledo, Christy A. Tremonti, Nicholas W. Troup, Sarah Tuttle, Eduardo Unda-Sanzana, Marica Valentini, Jaime Vargas-González, Mariana Vargas-Magaña, Jose Antonio Vázquez-Mata, M. Vivek, David Wake, Yuting Wang, Benjamin Alan Weaver, Anne-Marie Weijmans, Vivienne Wild, John C. Wilson, Robert F. Wilson, Nathan Wolthuis, W. M. Wood-Vasey, Renbin Yan, Meng Yang, Christophe Yèche, Olga Zamora, Pauline Zarrouk, Gail Zasowski, Kai Zhang, Cheng Zhao, Gongbo Zhao, Zheng Zheng, Guangtun Zhu, Hu Zou, Department of Physics, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Instituto de Astrofisica de Canarias (IAC), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Universidad Nacional Autónoma de México (UNAM), Department of Astrophysical Sciences [Princeton], Princeton University, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Department of Astronomy, Yale University [New Haven], University of Notre Dame [Indiana] (UND), Department of Physics and Astronomy [Philadelphia], University of Pennsylvania [Philadelphia], University of Wisconsin-Madison, Texas Tech University Health Sciences Center, Texas Tech University [Lubbock] (TTU), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - 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A. Baker Institute, Cornell University [New York], Institute of Infection, Immunity & Inflammation, University of Glasgow, Sainsbury Laboratory Cambridge University (SLCU), University of Cambridge [UK] (CAM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Carnegie Observatories, Carnegie Institution for Science [Washington], Institute of Science and Technology [Austria] (IST Austria), Universidad de Atacama, Department of Chemical and Biomolecular Engineering, Universidad de Antofagasta, Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Institute of cosmology and gravitation, University of Portsmouth, Institut d'Astronomie et d'Astrophysique [Bruxelles] (IAA), Université libre de Bruxelles (ULB), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Max-Planck-Institut für Astrophysik (MPA), 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(SKLCS), Institute of Software Chinese Academy of Sciences [Beijing], Nanjing University of Information Science and Technology (NUIST), Laboratoire de Chimie - UMR5182 (LC), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Institut de Chimie du CNRS (INC), Johns Hopkins University (JHU), Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), University of Pennsylvania, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Oxford-University of Oxford, University of California (UC)-University of California (UC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Universidad Autónoma de Madrid (UAM), University of Virginia, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), University of California [Irvine] (UC Irvine), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Bordeaux Montaigne (UBM)-Centre National de la Recherche Scientifique (CNRS), Carnegie Institution for Science, Institute of Science and Technology [Klosterneuburg, Austria] (IST Austria), Harvard University-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), University of Oxford, Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Ahumada R., Prieto C.A., Almeida A., Anders F., Anderson S.F., Andrews B.H., Anguiano B., Arcodia R., Armengaud E., Aubert M., Avila S., Avila-Reese V., Badenes C., Balland C., Barger K., Barrera-Ballesteros J.K., Basu S., Bautista J., Beaton R.L., Beers T.C., Benavides B.I.T., Bender C.F., Bernardi M., Bershady M., Beutler F., Bidin C.M., Bird J., Bizyaev D., Blanc G.A., Blanton M.R., Boquien M., Borissova J., Bovy J., Brandt W.N., Brinkmann J., Brownstein J.R., Bundy K., Bureau M., Burgasser A., Burtin E., Cano-Diaz M., Capasso R., Cappellari M., Carrera R., Chabanier S., Chaplin W., Chapman M., Cherinka B., Chiappini C., Doohyun Choi P., Chojnowski S.D., Chung H., Clerc N., Coffey D., Comerford J.M., Comparat J., Da Costa L., Cousinou M.-C., Covey K., Crane J.D., Cunha K., Ilha G.D.S., Dai Y.S., Damsted S.B., Darling J., Davidson J.W., Davies R., Dawson K., De N., De La Macorra A., De Lee N., Queiroz A.B.D.A., Deconto Machado A., De La Torre S., Dell'Agli F., Du Mas Des Bourboux H., Diamond-Stanic A.M., Dillon S., Donor J., Drory N., Duckworth C., Dwelly T., Ebelke G., Eftekharzadeh S., Davis Eigenbrot A., Elsworth Y.P., Eracleous M., Erfanianfar G., Escoffier S., Fan X., Farr E., Fernandez-Trincado J.G., Feuillet D., Finoguenov A., Fofie P., Fraser-Mckelvie A., Frinchaboy P.M., Fromenteau S., Fu H., Galbany L., Garcia R.A., Garcia-Hernandez D.A., Oehmichen L.A.G., Ge J., Maia M.A.G., Geisler D., Gelfand J., Goddy J., Gonzalez-Perez V., Grabowski K., Green P., Grier C.J., Guo H., Guy J., Harding P., Hasselquist S., Hawken A.J., Hayes C.R., Hearty F., Hekker S., Hogg D.W., Holtzman J.A., Horta D., Hou J., Hsieh B.-C., Huber D., Hunt J.A.S., Chitham J.I., Imig J., Jaber M., Angel C.E.J., Johnson J.A., Jones A.M., Jonsson H., Jullo E., Kim Y., Kinemuchi K., Kirkpatrick Iv C.C., Kite G.W., Klaene M., Kneib J.-P., Kollmeier J.A., Kong H., Kounkel M., Krishnarao D., Lacerna I., Lan T.-W., Lane R.R., Law D.R., Le Goff J.-M., Leung H.W., Lewis H., Li C., Lian J., Lin L., Long D., Longa-Peña P., Lundgren B., Lyke B.W., Ted Mackereth J., Macleod C.L., Majewski S.R., Manchado A., Maraston C., Martini P., Masseron T., Masters K.L., Mathur S., McDermid R.M., Merloni A., Merrifield M., Meszaros S., Miglio A., Minniti D., Minsley R., Miyaji T., Mohammad F.G., Mosser B., Mueller E.-M., Muna D., Muñoz-Gutierrez A., Myers A.D., Nadathur S., Nair P., Nandra K., Do Nascimento J.C., Nevin R.J., Newman J.A., Nidever D.L., Nitschelm C., Noterdaeme P., O'Connell J.E., Olmstead M.D., Oravetz D., Oravetz A., Osorio Y., Pace Z.J., Padilla N., Palanque-Delabrouille N., Palicio P.A., Pan H.-A., Pan K., Parker J., Paviot R., Peirani S., Ramrez K.P., Penny S., Percival W.J., Perez-Fournon I., Perez-Rafols I., Petitjean P., Pieri M.M., Pinsonneault M., Poovelil V.J., Povick J.T., Prakash A., Price-Whelan A.M., Raddick M.J., Raichoor A., Ray A., Rembold S.B., Rezaie M., Riffel R.A., Riffel R., Rix H.-W., Robin A.C., Roman-Lopes A., Roman-Zuñiga C., Rose B., Ross A.J., Rossi G., Rowlands K., Rubin K.H.R., Salvato M., Sanchez A.G., Sanchez-Menguiano L., Sanchez-Gallego J.R., Sayres C., Schaefer A., Schiavon R.P., Schimoia J.S., Schlafly E., Schlegel D., Schneider D.P., Schultheis M., Schwope A., Seo H.-J., Serenelli A., Shafieloo A., Shamsi S.J., Shao Z., Shen S., Shetrone M., Shirley R., Aguirre V.S., Simon J.D., Skrutskie M.F., Slosar A., Smethurst R., Sobeck J., Sodi B.C., Souto D., Stark D.V., Stassun K.G., Steinmetz M., Stello D., Stermer J., Storchi-Bergmann T., Streblyanska A., Stringfellow G.S., Stutz A., Suarez G., Sun J., Taghizadeh-Popp M., Talbot M.S., Tayar J., Thakar A.R., Theriault R., Thomas D., Thomas Z.C., Tinker J., Tojeiro R., Toledo H.H., Tremonti C.A., Troup N.W., Tuttle S., Unda-Sanzana E., Valentini M., Vargas-Gonzalez J., Vargas-Magaña M., Vazquez-Mata J.A., Vivek M., Wake D., Wang Y., Weaver B.A., Weijmans A.-M., Wild V., Wilson J.C., Wilson R.F., Wolthuis N., Wood-Vasey W.M., Yan R., Yang M., Yeche C., Zamora O., Zarrouk P., Zasowski G., Zhang K., Zhao C., Zhao G., Zheng Z., Zhu G., Zou H., Alfred P. Sloan Foundation, and Department of Energy (US)

Subjects
Optical telescopes, SAMPLE, Astrophysics, 01 natural sciences, Astronomi, astrofysik och kosmologi, Infrared astronomy, Observatory, Astronomy, Astrophysics and Cosmology, Astrophysics::Solar and Stellar Astrophysics, REDSHIFT 0.8, redshift surveys, stellar spectral lines, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, media_common, Astronomy databases, Redshift surveys, Physics, Astrophysics::Instrumentation and Methods for Astrophysics, stellar properties, CATALOG, astro-ph.CO, astronomy databases, Data release, [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], infrared astonomy, TELESCOPE, astro-ph.GA, media_common.quotation_subject, Astrophysics::Cosmology and Extragalactic Astrophysics, MASS, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Galactic abundances, Stellar properties, 0103 physical sciences, Astrophysics::Galaxy Astrophysics, DISTANCES, Stellar spectral lines, 010308 nuclear & particles physics, Astronomy and Astrophysics, optical telescopes, 115 Astronomy, Space science, Galaxy, GALAXY, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], STELLAR, 13. Climate action, Space and Planetary Science, Sky, [SDU]Sciences of the Universe [physics], galactic abundances, MILKY, astro-ph.IM, SDSS-IV MANGA
Abstract

This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17)., Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS website is www.sdss.org.

Published
2020

43. Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies

Author

F. de Gasperin, J. Vink, J. P. McKean, A. Asgekar, I. Avruch, M. J. Bentum, R. Blaauw, A. Bonafede, J. W. Broderick, M. Brüggen, F. Breitling, W. N. Brouw, H. R. Butcher, B. Ciardi, V. Cuciti, M. de Vos, S. Duscha, J. Eislöffel, D. Engels, R. A. Fallows, T. M. O. Franzen, M. A. Garrett, A. W. Gunst, J. Hörandel, G. Heald, M. Hoeft, M. Iacobelli, L. V. E. Koopmans, A. Krankowski, P. Maat, G. Mann, M. Mevius, G. Miley, R. Morganti, A. Nelles, M. J. Norden, A. R. Offringa, E. Orrú, H. Paas, V. N. Pandey, M. Pandey-Pommier, R. Pekal, R. Pizzo, W. Reich, A. Rowlinson, H. J. A. Rottgering, D. J. Schwarz, A. Shulevski, O. Smirnov, C. Sobey, M. Soida, M. Steinmetz, M. Tagger, M. C. Toribio, A. van Ardenne, A. J. van der Horst, M. P. van Haarlem, R. J. van Weeren, C. Vocks, O. Wucknitz, P. Zarka, P. Zucca, Astronomy, Kapteyn Astronomical Institute, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), De Gasperin F., Vink J., McKean J.P., Asgekar A., Avruch I., Bentum M.J., Blaauw R., Bonafede A., Broderick J.W., Bruggen M., Breitling F., Brouw W.N., Butcher H.R., Ciardi B., Cuciti V., De Vos M., Duscha S., Eisloffel J., Engels D., Fallows R.A., Franzen T.M.O., Garrett M.A., Gunst A.W., Horandel J., Heald G., Hoeft M., Iacobelli M., Koopmans L.V.E., Krankowski A., Maat P., Mann G., Mevius M., Miley G., Morganti R., Nelles A., Norden M.J., Offringa A.R., Orru E., Paas H., Pandey V.N., Pandey-Pommier M., Pekal R., Pizzo R., Reich W., Rowlinson A., Rottgering H.J.A., Schwarz D.J., Shulevski A., Smirnov O., Sobey C., Soida M., Steinmetz M., Tagger M., Toribio M.C., Van Ardenne A., Van Der Horst A.J., Van Haarlem M.P., Van Weeren R.J., Vocks C., Wucknitz O., Zarka P., Zucca P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Gravitation and Astroparticle Physics Amsterdam, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES)

Subjects
Astronomy, media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, radio continuum: general, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, radio continuum, law.invention, Telescope, law, 0103 physical sciences, Angular resolution, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Surface brightness, 010306 general physics, Cygnus A, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astrophysics - Astrophysics of Galaxies, interferometric [techniques], Cassiopeia A, techniques: interferometric, 13. Climate action, Space and Planetary Science, Sky, general, Astrophysics of Galaxies (astro-ph.GA), interferometric, ddc:520, general [radio continuum], Radio frequency, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], techniques, general [ontinuum]
Abstract

The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (, 7 pages, 2 figures, accepted A&A, online data on A&A website

Published
2020

44. Nearly all the sky is covered by Lyman-alpha emission around high redshift galaxies

Author

S. Cantalupo, Peter M. Weilbacher, Philipp Richter, R. Saust, J. Kerutt, Jarle Brinchmann, Floriane Leclercq, Lutz Wisotzki, Johan Richard, E. C. Herenz, Tanya Urrutia, T. Contini, Mohammad Akhlaghi, Nicolas Bouché, Matthias Steinmetz, Themiya Nanayakkara, Raffaella Anna Marino, Joop Schaye, Hanae Inami, A. Monreal-Ibero, Martin Wendt, Kasper B. Schmidt, B. Guiderdoni, Roland Bacon, Michael V. Maseda, Wisotzki, L, Bacon, R, Brinchmann, J, Cantalupo, S, Richter, P, Schaye, J, Schmidt, K, Urrutia, T, Weilbacher, P, Akhlaghi, M, Bouche, N, Contini, T, Guiderdoni, B, Herenz, E, Inami, H, Kerutt, J, Leclercq, F, Marino, R, Maseda, M, Monreal-Ibero, A, Nanayakkara, T, Richard, J, Saust, R, Steinmetz, M, and Wendt, M

Subjects
media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spectral line, 0103 physical sciences, ddc:530, Surface brightness, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, Physics, Very Large Telescope, Multidisciplinary, Line-of-sight, 010308 nuclear & particles physics, galaxie, Institut für Physik und Astronomie, Quasar, Astrophysics - Astrophysics of Galaxies, Redshift, Galaxy, 3. Good health, Cosmology, Galaxies and clusters, 13. Climate action, Sky, Astrophysics of Galaxies (astro-ph.GA)
Abstract

Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, fed by inflows from the intergalactic medium and by outflows due to galactic winds. Absorption-line measurements along the sightlines to bright and rare background quasars indicate that this circumgalactic medium pervades far beyond the extent of starlight in galaxies, but very little is known about the spatial distribution of this gas. A new window into circumgalactic environments was recently opened with the discovery of ubiquitous extended Lyman-alpha emission from hydrogen around high-redshift galaxies, facilitated by the extraordinary sensitivity of the MUSE instrument at the ESO Very Large Telescope. Due to the faintness of this emission, such measurements were previously limited to especially favourable systems or to massive statistical averaging. Here we demonstrate that low surface brightness Lyman-alpha emission surrounding faint galaxies at redshifts between 3 and 6 adds up to a projected sky coverage of nearly 100%. The corresponding rate of incidence (the mean number of Lyman-alpha emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high column density absorbers frequently detected in the spectra of distant quasars. This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected also in emission., published in Nature, online on 01 Oct 2018, in print on 11 Oct 2018. This is the Authors' version, for the published version see https://www.nature.com/articles/s41586-018-0564-6 ; free viewing access via https://rdcu.be/8eCx

Published
2018

45. CHROMOSPHERICALLY ACTIVE STARS in the RAVE SURVEY. II. YOUNG DWARFS in the SOLAR NEIGHBORHOOD

Author

Andrea Kunder, Alessandro Siviero, Matthias Steinmetz, Gerard Gilmore, J. Wojno, Warren A. Reid, Brad K. Gibson, Quentin A. Parker, R. F. G. Wyse, Joss Bland-Hawthorn, Julio F. Navarro, Tomaž Zwitter, C. Conrad, Olivier Bienaymé, G. Matijevič, Fred G. Watson, Ulisse Munari, Maruša Žerjal, Kenneth C. Freeman, Eva K. Grebel, George M. Seabroke, Georges Kordopatis, Žerjal, M [0000-0001-6023-4974], Zwitter, T [0000-0002-2325-8763], Grebel, EK [0000-0002-1891-3794], Munari, U [0000-0001-6805-9664], Steinmetz, M [0000-0001-6516-7459], Bland-Hawthorn, J [0000-0001-7516-4016], Gibson, BK [0000-0003-4446-3130], Gilmore, G [0000-0003-4632-0213], Kunder, A [0000-0002-2808-1370], and Apollo - University of Cambridge Repository

Subjects
stars: chromospheres, Emission flux, Field (physics), Infrared, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: pre-main sequence, 01 natural sciences, 0103 physical sciences, stars: activity, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Star formation, Astronomy and Astrophysics, Stars, Young age, stars: emission-line, Be, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Age estimation, Astrophysics::Earth and Planetary Astrophysics, catalogs, Dynamo
Abstract

A large sample of over 38,000 chromospherically active candidate solar-like stars and cooler dwarfs from the RAVE survey is addressed in this paper. An improved activity identification with respect to the previous study was introduced to build a catalog of field stars in the Solar neighborhood with an excess emission flux in the calcium infrared triplet wavelength region. The central result of this work is the calibration of the age--activity relation for the main sequence dwarfs in a range from a few $10 \; \mathrm{Myr}$ up to a few Gyr. It enabled an order of magnitude age estimation of the entire active sample. Almost 15,000 stars are shown to be younger than $1\;\mathrm{Gyr}$ and $\sim$2000 younger than $100\;\mathrm{Myr}$. The young age of the most active stars is confirmed by their position off the main sequence in the $J-K$ versus $N_{UV}-V$ diagram showing strong ultraviolet excess, mid-infrared excess in the $J-K$ versus $W_1-W_2$ diagram and very cool temperatures ($J-K>0.7$). They overlap with the reference pre-main sequence RAVE stars often displaying X-ray emission. The activity level increasing with the color reveals their different nature from the solar-like stars and probably represents an underlying dynamo generating magnetic fields in cool stars. 50\% of the RAVE objects from DR5 are found in the TGAS catalog and supplemented with accurate parallaxes and proper motions by Gaia. This makes the database of a large number of young stars in a combination with RAVE's radial velocities directly useful as a tracer of the very recent large-scale star formation history in the Solar neighborhood. The data are available online in the Vizier database., 21 pages, 14 figures, accepted to ApJ

Published
2018
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46. LOFAR discovery of a quiet emission mode in PSR B0823+26

Author

F. Breitling, Gottfried Mann, R. Pizzo, John D. Anderson, Cees Bassa, Sera Markoff, Rene P. Breton, Ashish Asgekar, Charlotte Sobey, E. Jütte, George Heald, Heino Falcke, P. Maat, M. J. Norden, M. A. Garrett, Jean-Mathias Grießmeier, Ph. Zarka, Rebecca McFadden, H. Paas, Ben Stappers, E. de Geus, Sarod Yatawatta, V. I. Kondratiev, D. D. Mulcahy, J. van Leeuwen, S. ter Veen, M. Pilia, M. Pandey-Pommier, Ralph A. M. J. Wijers, A. W. Gunst, J. Sluman, Olaf Wucknitz, H. J. A. Röttgering, Philip Best, Christian Vocks, D. McKay-Bukowski, Michel Tagger, D. Carbone, A. Alexov, Andrew Lyne, Antonia Rowlinson, A. Noutsos, Adam Stewart, Chiara Ferrari, T. E. Hassall, Evan Keane, Patrick Weltevrede, Jason W. T. Hessels, Satyendra Thoudam, S. Duscha, M. Serylak, A. van Duin, G. Pietka, Laura Birzan, Jochen Eislöffel, J. P. Hamaker, Wilfred Frieswijk, C. Toribio, Michael Kramer, D. A. Rafferty, A. G. Polatidis, Arthur Corstanje, A. Nelles, John D. Swinbank, Y. Tang, Anna M. M. Scaife, Martin Bell, N. J. Young, V. N. Pandey, Gerard H. Kuper, Cyril Tasse, J. W. Broderick, H. Munk, John McKean, Marcus Brüggen, Matthias Steinmetz, Annalisa Bonafede, A. Renting, Richard Fallows, R. Vermeulen, Mark J. Bentum, Matthias Hoeft, M. de Vos, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, Rob Fender, Oleg Smirnov, Emanuela Orru, Dominik J. Schwarz, I. M. Avruch, Anna V. Bilous, R. J. van Weeren, Sobey, C., Young, N.J., Hessels, J.W.T., Weltevrede, P., Noutsos, A., Stappers, B.W., Kramer, M., Bassa, C., Lyne, A.G., Kondratiev V.I., null, Hassall, T.E., Keane, E.F., Bilous, A.V., Breton, R.P., Grießmeier, J.M., Karastergiou, A., Pilia, M., Serylak, M., Ter Veen, S., Van Leeuwen, J., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Best, P., Bĭrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Corstanje, A., Carbone, D., De Geus, E., De Vos, M., Van Duin, A., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Gunst, A.W., Hamaker, J.P., Heald, G., Hoeft, M., Hörandel, J., Jütte, E., Kuper, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orrù, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Rafferty, D., Renting, A., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Max-Planck-Institut für Radioastronomie (MPIFR), University of Minnesota [Twin Cities] (UMN), University of Minnesota System, University of Amsterdam [Amsterdam] (UvA), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Columbia Astrophysics Laboratory (CAL), Columbia University [New York], Cornell University [New York], Netherlands Institute for Radio Astronomy (ASTRON), Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Oxford Astrophysics, University of Oxford, Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Département de Géologie, Université de Montréal (UdeM), University Bochum, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, We would like to thank R. Karuppusamy for his help with the Effelsberg observations. CF acknowledges financial support by the Agence Nationale de la Recherche through grant ANR-09-JCJC-0001-01., European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), ITA, GBR, FRA, DEU, NLD, Radboud university [Nijmegen], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
stars, PSR B0823+26-radio telescopes, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Pulsar planet, FOS: Physical sciences, neutron- pulsars, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, neutron [stars], Pulsar, Millisecond pulsar, Pulsars: individual: PSR B0823+26, individual, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Astroparticle physics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Stars: neutron, Stars, Neutron star, Astrophysics - Solar and Stellar Astrophysics, magnetosphere-pulsars, [SDU]Sciences of the Universe [physics], Space and Planetary Science, QUIET, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, individual: PSR B0823+26 [pulsars]
Abstract

PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight into the relationship between these various emission phenomena and what they might teach us about pulsar magnetospheres. Here we report on the LOFAR discovery that PSR B0823+26 has a weak and sporadically emitting 'quiet' (Q) emission mode that is over 100 times weaker (on average) and has a nulling fraction forty-times greater than that of the more regularly-emitting 'bright' (B) mode. Previously, the pulsar has been undetected in the Q-mode, and was assumed to be nulling continuously. PSR B0823+26 shows a further decrease in average flux just before the transition into the B-mode, and perhaps truly turns off completely at these times. Furthermore, simultaneous observations taken with the LOFAR, Westerbork, Lovell, and Effelsberg telescopes between 110 MHz and 2.7 GHz demonstrate that the transition between the Q-mode and B-mode occurs within one single rotation of the neutron star, and that it is concurrent across the range of frequencies observed., Comment: 15 pages, 8 figures, 2 tables, accepted for publication in MNRAS

Published
2015

47. PLATO as it is: a legacy mission for Galactic archaeology

Author

A. Miglio, C. Chiappini, B. Mosser, G. R. Davies, K. Freeman, L. Girardi, P. Jofré, D. Kawata, B. M. Rendle, M. Valentini, L. Casagrande, W. J. Chaplin, G. Gilmore, K. Hawkins, B. Holl, T. Appourchaux, K. Belkacem, D. Bossini, K. Brogaard, M.‐J. Goupil, J. Montalbán, A. Noels, F. Anders, T. Rodrigues, G. Piotto, D. Pollacco, H. Rauer, C. Allende Prieto, P. P. Avelino, C. Babusiaux, C. Barban, B. Barbuy, S. Basu, F. Baudin, O. Benomar, O. Bienaymé, J. Binney, J. Bland‐Hawthorn, A. Bressan, C. Cacciari, T. L. Campante, S. Cassisi, J. Christensen‐Dalsgaard, F. Combes, O. Creevey, M. S. Cunha, R. S. Jong, P. Laverny, S. Degl'Innocenti, S. Deheuvels, É. Depagne, J. Ridder, P. Di Matteo, M. P. Di Mauro, M.‐A. Dupret, P. Eggenberger, Y. Elsworth, B. Famaey, S. Feltzing, R. A. García, O. Gerhard, B. K. Gibson, L. Gizon, M. Haywood, R. Handberg, U. Heiter, S. Hekker, D. Huber, R. Ibata, D. Katz, S. D. Kawaler, H. Kjeldsen, D. W. Kurtz, N. Lagarde, Y. Lebreton, M. N. Lund, S. R. Majewski, P. Marigo, M. Martig, S. Mathur, I. Minchev, T. Morel, S. Ortolani, M. H. Pinsonneault, B. Plez, P. G. Prada Moroni, D. Pricopi, A. Recio‐Blanco, C. Reylé, A. Robin, I. W. Roxburgh, M. Salaris, B. X. Santiago, R. Schiavon, A. Serenelli, S. Sharma, V. Silva Aguirre, C. Soubiran, M. Steinmetz, D. Stello, K. G. Strassmeier, P. Ventura, R. Ventura, N. A. Walton, C. C. Worley, Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Arizona State University [Tempe] (ASU), Leibniz-Institut für Astrophysik Potsdam (AIP), Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], Heckscher-Klinikum, Danish AsteroSeismology Centre (DASC), Universidade Federal de São Paulo (UNIFESP), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Department of Astronomy [New Haven], Yale University [New Haven], Evolution et Modélisation des Bassins Sédimentaires (EMBS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Department of Biomedical, Metabolic and Neural Sciences [Modena], Chaire Galaxies et cosmologie, Collège de France (CdF (institution)), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universidade de Aveiro, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Las Cumbres Observatory (LCO), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Université de Strasbourg (UNISTRA), Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universitat de Girona (UdG), Max-Planck-Institut für Extraterrestrische Physik (MPE), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, SETI Institute, University of Illinois at Urbana Champaign (UIUC), University of Illinois at Urbana-Champaign [Urbana], University of Illinois System-University of Illinois System, Universidade Federal de Santa Catarina = Federal University of Santa Catarina [Florianópolis] (UFSC), Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Space Science Institute [Boulder] (SSI), Department of Astronomy (Ohio State University), Ohio State University [Columbus] (OSU), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Astrophysical Research Institute [Liverpool], Liverpool John Moore University (ljmu), Institute of Space Sciences [Barcelona] (ICE-CSIC), Spanish National Research Council [Madrid] (CSIC), Sydney Institute for Astronomy (SIfA), The University of Sydney, M2A 2017, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leibniz Institute for Astrophysics Potsdam (AIP), Symbiose Marine (SM), Evolution Paris Seine, Université des Antilles et de la Guyane (UAG)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles et de la Guyane (UAG)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), DNRF106, The Danish National Research Foundation, Centre National d’Etudes Spatiales, PRIN INAF 2014 - CRA 1.05.01.94.05, Science and Technology Facilities Council, Programme National Cosmologie et Galaxies (CNRS/INSU, France), IF/00894/2012/, Federación Española de Enfermedades Raras, CNES Fellowship, 615604, ERC Consolidator (STARKEY), Federaal Wetenschapsbeleid, ESP2015-66134-R, Ministerio de Economía y Competitividad, European Commission's Seventh Framework Programme, Swedish National Space Board, European Commission, DLR, FT1400147, Australian Research Council, NNX16AI09G, National Aeronautics and Space Administration, European Cooperation in Science and Technology, CH1188/2-1, DFG, CA16117, ChETEC COST Action, 10118, Villum Fonden, European Union FP7 program, 320360, ERC, UID/FIS/04434/2013, FCT, G1502, NYUAD Institute, Programme National de Physique Stellaire (PNPS), ITA, USA, GBR, FRA, DEU, ESP, Federal University of Sao Paulo (Unifesp), Université Paris-Saclay, Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Collège de France - Chaire Galaxies et cosmologie, Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Genève = University of Geneva (UNIGE), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, University of Illinois System, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université des Antilles et de la Guyane (UAG)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles et de la Guyane (UAG)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), Miglio A., Chiappini C., Mosser B., Davies G.R., Freeman K., Girardi L., Jofre P., Kawata D., Rendle B.M., Valentini M., Casagrande L., Chaplin W.J., Gilmore G., Hawkins K., Holl B., Appourchaux T., Belkacem K., Bossini D., Brogaard K., Goupil M.-J., Montalban J., Noels A., Anders F., Rodrigues T., Piotto G., Pollacco D., Rauer H., Prieto C.A., Avelino P.P., Babusiaux C., Barban C., Barbuy B., Basu S., Baudin F., Benomar O., Bienayme O., Binney J., Bland-Hawthorn J., Bressan A., Cacciari C., Campante T.L., Cassisi S., Christensen-Dalsgaard J., Combes F., Creevey O., Cunha M.S., Jong R.S., Laverny P., Degl'Innocenti S., Deheuvels S., Depagne E., Ridder J., Matteo P.D., Mauro M.P.D., Dupret M.-A., Eggenberger P., Elsworth Y., Famaey B., Feltzing S., Garcia R.A., Gerhard O., Gibson B.K., Gizon L., Haywood M., Handberg R., Heiter U., Hekker S., Huber D., Ibata R., Katz D., Kawaler S.D., Kjeldsen H., Kurtz D.W., Lagarde N., Lebreton Y., Lund M.N., Majewski S.R., Marigo P., Martig M., Mathur S., Minchev I., Morel T., Ortolani S., Pinsonneault M.H., Plez B., Moroni P.G.P., Pricopi D., Recio-Blanco A., Reyle C., Robin A., Roxburgh I.W., Salaris M., Santiago B.X., Schiavon R., Serenelli A., Sharma S., Aguirre V.S., Soubiran C., Steinmetz M., Stello D., Strassmeier K.G., Ventura P., Ventura R., Walton N.A., Worley C.C., Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Université Nice Sophia Antipolis (... - 2019) (UNS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles et de la Guyane (UAG)-Université Pierre et Marie Curie - Paris 6 (UPMC)

Subjects
RED-GIANT STARS, Astrophysics, 01 natural sciences, COROT ASTEROSEISMOLOGY FIELDS, Astrophysics::Solar and Stellar Astrophysics, VELOCITY EXPERIMENT RAVE, Galaxy: structure, 010303 astronomy & astrophysics, SUN-LIKE STAR, QC, QB, Physics, structure - stars: abundances - stars: fundamental parameters - stars: oscillations - surveys [Galaxy], Astrophysics - Solar and Stellar Astrophysics, stars: fundamental parameters, stars: oscillations, Astrophysics::Earth and Planetary Astrophysics, SOLAR-LIKE OSCILLATIONS, THICK DISK, stars: abundances, Relation (database), DATA RELEASE, Milky Way, surveys, Astronomy and Astrophysics, Space and Planetary Science, FOS: Physical sciences, MILKY-WAY DISK, F500, Kepler, Asteroseismology, ATMOSPHERIC PARAMETERS, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Quality (philosophy), Galaxy: structure â stars: abundances â stars: fundamental parameters â stars: oscillations â surveys, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, Galaxy: structure – stars: abundances – stars: fundamental parameters – stars: oscillations – surveys, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Data science, Astrophysics - Astrophysics of Galaxies, Galaxy, COLD DARK-MATTER, Stars, Astrophysics of Galaxies (astro-ph.GA), Stellar physics, Galaxy: structure – stars: abundances – stars: fundamental parameters – stars: oscillations – surveys, Galaxy: structure - stars: abundances - stars: fundamental parameters - stars: oscillations - surveys
Abstract

Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but will only enable a blurred view on the temporal sequence that led to the present-day Galaxy. As demonstrated by the (ongoing) exploitation of data from the pioneering photometric missions CoRoT, Kepler, and K2, asteroseismology provides the way forward: solar-like oscillating giants are excellent evolutionary clocks thanks to the availability of seismic constraints on their mass and to the tight age-initial-mass relation they adhere to. In this paper we identify five key outstanding questions relating to the formation and evolution of the Milky Way that will need precise and accurate ages for large samples of stars to be addressed, and we identify the requirements in terms of number of targets and the precision on the stellar properties that are needed to tackle such questions. By quantifying the asteroseismic yields expected from PLATO for red-giant stars, we demonstrate that these requirements are within the capabilities of the current instrument design, provided that observations are sufficiently long to identify the evolutionary state and allow robust and precise determination of acoustic-mode frequencies. This will allow us to harvest data of sufficient quality to reach a 10% precision in age. This is a fundamental pre-requisite to then reach the more ambitious goal of a similar level of accuracy, which will only be possible if we have to hand a careful appraisal of systematic uncertainties on age deriving from our limited understanding of stellar physics, a goal which conveniently falls within the main aims of PLATO's core science., 17 pages, 9 figures, accepted for publication in Astronomical Notes

Published
2017

48. Synchronous X-ray and Radio Mode Switches: A Rapid Global Transformation of the Pulsar Magnetosphere

Author

Y. Tang, Anna M. M. Scaife, Steve Rawlings, Aris Karastergiou, Michael W. Wise, Harvey Butcher, B. Ciardi, S. Duscha, V. N. Pandey, Gianni Bernardi, John McKean, Charlotte Sobey, Emanuela Orrú, Chiara Ferrari, M. Kuniyoshi, H. Munk, Marcus Brüggen, Michael Kramer, Cyril Tasse, J. W. Broderick, E. de Geus, Ashish Asgekar, Jason W. T. Hessels, F. de Gasperin, Matthias Hoeft, George Heald, L. Kuiper, A. P. Schoenmakers, P. Maat, R. H. van de Brink, Sera Markoff, Dipanjan Mitra, Philip Best, G. Wright, Ralph A. M. J. Wijers, J. de Plaa, Heino Falcke, V. I. Kondratiev, Rahul Basu, A. Noutsos, T. Coenen, Benjamin Stappers, Michel Tagger, Frank Breitling, Giulia Macario, Rob Fender, Rene C. Vermeulen, Michael R. Bell, F. Batejat, A. Alexov, Marco Iacobelli, H. Paas, Sarod Yatawatta, Patrick Weltevrede, Tim Hassall, R. J. van Weeren, W. Reich, M. Pilia, Laura Birzan, W. Hermsen, Evan Keane, Aleksandar Shulevski, Mark J. Bentum, M. Serylak, Martin Bell, Annalisa Bonafede, J. van Leeuwen, A. Horneffer, Jochen Eislöffel, Maaijke Mevius, H. J. A. Röttgering, A. G. Polatidis, R. Morganti, I. M. Avruch, S. ter Veen, A. W. Gunst, Olaf Wucknitz, Matthias Steinmetz, M. Pandey-Pommier, K. Zagkouris, J. Sluman, Roberto Pizzo, Jean-Mathias Grießmeier, G. Kuper, Philippe Zarka, Joanna M. Rankin, M. A. Garrett, James Miller-Jones, Wilfred Frieswijk, Hermsen, W., Hessels, J.W.T., Kuiper, L., Van Leeuwen, J., Mitra, D., De Plaa, J., Rankin, J.M., Stappers, B.W., Wright, G.A.E., Basu, R., Alexov, A., Coenen, T., Grießmeier, J.-M., Hassall, T.E., Karastergiou, A., Keane, E., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Noutsos, A., Serylak, M., Pilia, M., Sobey, C., Weltevrede, P., Zagkouris, K., Asgekar, A., Avruch, I.M., Batejat, F., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Duscha, S., Eislöffel, J., Falcke, H., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., De Gasperin, F., De Geus, E., Gunst, A.W., Heald, G., Hoeft, M., Horneffer, A., Iacobelli, M., Kuper, G., Maat, P., Macario, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Morganti, R., Munk, H., Orrú, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Rawlings, S., Reich, W., Röttgering, H., Scaife, A.M.M., Schoenmakers, A., Shulevski, A., Sluman, J., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van De Brink, R.H., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., SRON Netherlands Institute for Space Research (SRON), University of Amsterdam [Amsterdam] (UvA), National Centre for Radio Astrophysics [Pune] (NCRA), Tata Institute for Fundamental Research (TIFR), University of Vermont [Burlington], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Astronomy Centre, University of Sussex, Space Telescope Science Institute (STSci), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Oxford Astrophysics, University of Oxford, Centre for Astrophysics and Supercomputing, Swinburne University of Technology [Melbourne], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Kapteyn Astronomical Institute, Astronomy, Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Electromagnetic field, POLARIZATION, Electromagnetic spectrum, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Magnetosphere, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, EMPIRICAL-THEORY, 01 natural sciences, Binary pulsar, Pulsar, Millisecond pulsar, 0103 physical sciences, 010306 general physics, XMM-NEWTON OBSERVATIONS, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, DRIFTING SUBPULSES, Multidisciplinary, B0943+10, Polarization (waves), GAMMA-RAY, [SDU]Sciences of the Universe [physics], 13. Climate action, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, RADIATION, EMISSION, Astrophysics - High Energy Astrophysical Phenomena, PHOTON IMAGING CAMERA, POWERED PULSARS, Radio wave
Abstract

Pulsars emit low-frequency radio waves through to high-energy gamma-rays that are generated anywhere from the surface out to the edges of the magnetosphere. Detecting correlated mode changes in the multi-wavelength emission is therefore key to understanding the physical relationship between these emission sites. Through simultaneous observations, we have detected synchronous switching in the radio and X-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio 'bright' mode, the X-rays show only an un-pulsed, non-thermal component. Conversely, when the pulsar is in a radio 'quiet' mode, the X-ray luminosity more than doubles and a 100%-pulsed thermal component is observed along with the non-thermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories., Paper published in Science including supplementary material

Published
2013

49. Muse Gas Flow and Wind (MEGAFLOW). I. First MUSE Results on Background Quasars

Author

Simon J. Lilly, Matthias Steinmetz, Ilane Schroetter, Johan Richard, Hayley Finley, Joop Schaye, Sebastiano Cantalupo, Roland Bacon, Martin Wendt, Nicolas Bouché, R. A. Marino, Kurt T. Soto, Lorrie A. Straka, Lutz Wisotzki, Thierry Contini, Roser Pello, Schroetter, I, Bouche, N, Wendt, M, Contini, T, Finley, H, Pello, R, Bacon, R, Cantalupo, S, Marino, R, Richard, J, Lilly, S, Schaye, J, Soto, K, Steinmetz, M, Straka, L, and Wisotzki, L

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, quasars: individual (SDSS J213748+001220, SDSS J215200+062516), 01 natural sciences, 0103 physical sciences, Galaxy formation and evolution, galaxies: formation, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Spectrograph, Astrophysics::Galaxy Astrophysics, Physics, Very Large Telescope, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Institut für Physik und Astronomie, Astronomy and Astrophysics, Quasar, Escape velocity, Multi Unit Spectroscopic Explorer, Astrophysics - Astrophysics of Galaxies, Galaxy, Stars, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), intergalactic medium, galaxies: evolution
Abstract

The physical properties of galactic winds are one of the keys to understand galaxy formation and evolution. These properties can be constrained thanks to background quasar lines of sight (LOS) passing near star-forming galaxies (SFGs). We present the first results of the MusE GAs FLOw and Wind (MEGAFLOW) survey obtained of 2 quasar fields which have 8 MgII absorbers of which 3 have rest-equivalent width greater than 0.8 \AA. With the new Multi Unit Spectroscopic Explorer (MUSE) spectrograph on the Very Large Telescope (VLT), we detect 6 (75$\%$) MgII host galaxy candidates withing a radius of 30 arcsec from the quasar LOS. Out of these 6 galaxy--quasar pairs, from geometrical arguments, one is likely probing galactic outflows, two are classified as "ambiguous", two are likely probing extended gaseous disks and one pair seems to be a merger. We focus on the wind$-$pair and constrain the outflow using a high resolution quasar spectra from Ultraviolet and Visual Echelle Spectrograph (UVES). Assuming the metal absorption to be due to gas flowing out of the detected galaxy through a cone along the minor axis, we find outflow velocities of the order of $\approx$ 150 km/s (i.e. smaller than the escape velocity) with a loading factor, $\eta =\dot M_{\rm out}/$SFR, of $\approx$ 0.7. We see evidence for an open conical flow, with a low-density inner core. In the future, MUSE will provide us with about 80 multiple galaxy$-$quasar pairs in two dozen fields., Comment: 20 pages, 16 figures, accepted for publication in ApJ

Published
2016

50. Mergers and the outside-in formation of dwarf spheroidals

Author

Julio F. Navarro, Matthias Steinmetz, M. G. Abadi, Yehuda Hoffman, Gustavo Yepes, Stefan Gottlöber, Alejandro Benítez-Llambay, Benitez-Llambay, A, Navarro, J, Abadi, M, Gottlöber, S, Yepes, G, Hoffman, Y, Steinmetz, M, and UAM. Departamento de Física Teórica

Subjects
endocrine system, Stellar population, Metallicity, Population, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Galaxies: formation, 01 natural sciences, Dark ages, reionization, first stars, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Local group, education, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, First episode, Physics, education.field_of_study, 010308 nuclear & particles physics, Star formation, Galaxies: dwarf, Astronomy, Local Group, Física, Galaxies: evolution, Astronomy and Astrophysics, evolution [Galaxies], Galaxies: stellar content, Astrophysics - Astrophysics of Galaxies, formation [Galaxies], Galaxy, Accretion (astrophysics), dwarf [Galaxies], Dark ages, reionization, first star, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), stellar content [Galaxies], Astrophysics::Earth and Planetary Astrophysics
Abstract

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved, We use a cosmological simulation of the formation of the Local Group to explore the origin of age and metallicity gradients in dwarf spheroidal galaxies.We find that a number of simulated dwarfs form 'outside-in', with an old, metal-poor population that surrounds a younger, more concentrated metal-rich component, reminiscent of dwarf spheroidals like Sculptor or Sextans. We focus on a few examples where stars form in two populations distinct in age in order to elucidate the origin of these gradients. The spatial distributions of the two components reflect their diverse origin; the old stellar component is assembled through mergers, but the young population forms largely in situ. The older component results from a first episode of star formation that begins early but is quickly shut off by the combined effects of stellar feedback and reionization. The younger component forms when a late accretion event adds gas and reignites star formation. The effect of mergers is to disperse the old stellar population, increasing their radius and decreasing their central density relative to the young population. We argue that dwarf-dwarf mergers offer a plausible scenario for the formation of systems with multiple distinct populations and, more generally, for the origin of age and metallicity gradients in dwarf spheroidals, Our collaboration has been supported by DFG grants GO 563/21-1 and GO 563/24-1 as well as by CONICET. ABL, JFN and MGA aknowledge support from ANPCyT grant PICT2012- 1137. GY acknowledges support from he Spanish MINECO under research grants AYA2012-31101 and FPA2012-34694. YH has been partially supported by the Israel Science Foundation (1013/12)

Published
2016

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