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1. Titanium abundances in late-type stars, II. Grid of departure coefficients and application to a sample of $70\,000$ stars

Author

Mallinson, J. W. E., Lind, K., Amarsi, A. M., and Youakim, K.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

Rapidly growing datasets from stellar spectroscopic surveys are providing unprecedented opportunities to analyse the chemical evolution history of our Galaxy. However, spectral analysis requires accurate modelling of synthetic stellar spectra for late-type stars, for which the assumption of local thermodynamic equilibrium (LTE) has been shown to be insufficient in many cases. Errors associated with LTE can be particularly large for Ti I, which is susceptible to over-ionisation, particularly in metal-poor stars. The aims of this work are to study and quantify the 1D non-LTE effects on titanium abundances across the Hertzsprung-Russell diagram for a large sample of stars. A large grid of departure coefficients, $\beta_\nu$, were computed on standard MARCS model atmospheres. The grid extends from 3000K to 8000K in T$_{\mathrm{eff}}$, -0.5 to +5.5 dex in log(g), and -5.0 to +1.0 in [Fe/H], with non-LTE effects in this grid reaching up to 0.4 dex. This was used to compute abundance corrections that were subsequently applied to the LTE abundances of over 70,000 stars selected from the GALAH survey and additional metal-poor dwarfs. The non-LTE effects grow towards lower [Fe/H], lower log(g), and higher T$_{\mathrm{eff}}$, with a minimum and maximum $\Delta$A(Ti I) of 0.02 and 0.19 in the GALAH sample. For metal-poor giants, the non-LTE modelling reduces the average ionisation imbalance from -0.11 dex to -0.01 dex at [Fe/H] = -1.7, and the enhancement in titanium abundances from Ti I lines results in a [Ti/Fe] versus [Fe/H] trend that more closely resembles the behaviour of Ti II at low metallicities. Non-LTE effects on titanium abundances are significant. Neglecting them may alter our understanding of Galactic chemical evolution. We have made our grid of departure coefficients publicly available, with the caveat that the Ti abundances of metal-poor dwarfs need further study in 3D non-LTE.

Published
2024

2. Beyond Gaia DR3: Tracing the [$\alpha$/M]-[M/H] bimodality from the inner to the outer Milky Way disc with Gaia-RVS and convolutional neural networks

Author

Guiglion, G., Nepal, S., Chiappini, C., Khoperskov, S., Traven, G., Queiroz, A. B. A., Steinmetz, M., Valentini, M., Fournier, Y., Vallenari, A., Youakim, K., Bergemann, M., Mészáros, S., Lucatello, S., Sordo, R., Fabbro, S., Minchev, I., Tautvaišienė, G., Mikolaitis, Š., and Montalbán, J.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

In June 2022, Gaia DR3 has provided the astronomy community with about one million spectra from the Radial Velocity Spectrometer (RVS) covering the CaII triplet region. However, one-third of the published spectra have 15

Published
2023

3. Titanium abundances in late-type stars I. 1D non-local thermodynamic equilibrium modelling in benchmark dwarfs and giants

Author

Mallinson, J. W. E., Lind, K., Amarsi, A. M., Barklem, P. S., Grumer, J., Belyaev, A. K., and Youakim, K.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The titanium abundances of late-type stars are important tracers of Galactic formation history. However, abundances inferred from Ti I and Ti II lines can be in stark disagreement in very metal-poor giants. Departures from local thermodynamic equilibrium (LTE) have a large impact on the minority neutral species and thus influences the ionisation imbalance, but satisfactory non-LTE modelling for both dwarfs and giants has not been achieved in previous literature. The reliability of titanium abundances is reassessed in benchmark dwarfs and giants using a new non-LTE model and one-dimensional (1D) model atmospheres. A comprehensive model atom was compiled with a more extended level structure and newly published data for inelastic collisions between Ti I and neutral hydrogen. In 1D LTE, the Ti I and Ti II lines agree to within $0.06$ dex for the Sun, Arcturus, and the very metal-poor stars HD84937 and HD140283. For the very metal-poor giant HD122563, the Ti I lines give an abundance that is $0.47$ dex lower than that from Ti II. The 1D non-LTE corrections can reach $+0.4$ dex for individual Ti I lines and $+0.1$ dex for individual Ti II lines, and reduce the overall ionisation imbalance to $-0.17$ dex for HD122563. However, it also increases the imbalance for the very metal-poor dwarf and sub-giant to around $0.2$ dex. Using 1D non-LTE reduces the ionisation imbalance in very metal-poor giants but breaks the balance of other very metal-poor stars, consistent with the conclusions in earlier literature. To make further progress, consistent 3D non-LTE models are needed., Comment: 9 pages plus appendix, 6 figures; accepted for publication in Astronomy & Astrophysics

Published
2022
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4. The Pristine survey VIII: The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime

Author

Youakim, K., Starkenburg, E., Martin, N. F., Matijevic, G., Aguado, D. S., Prieto, C. Allende, Arentsen, A., Bonifacio, P., Carlberg, R. G., Hernández, J. I. González, Hill, V., Kordopatis, G., Lardo, C., Navarro, J. F., Jablonka, P., Janssen, R. Sánchez, Sestito, F., and Thomas, G. F.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ([Fe/H] < -3), and currently consists of over 4 million FGK-type stars over a sky area of $\sim 2~500\, \mathrm{deg}^2$. We focus our analysis on a subsample of $\sim 80~000$ main sequence turnoff stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at [Fe/H] = -1.6, and a slope of $\Delta$(LogN)/$\Delta[Fe/H] = 1.0 \pm 0.1$ in the metallicity range of -3.4 < [Fe/H] < -2.5. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low latitude field in the anticenter direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for [Fe/H] < -2.5 and 1.5 for [Fe/H] < -3, suggesting that the lack of low metallicity globular clusters in the Milky Way is not due simply to statistical undersampling., Comment: 17 pages, 12 figures, 5 tables, accepted for publication in MNRAS

Published
2020
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5. Kinematics with Gaia DR2: The Force of a Dwarf

Author

Carrillo, I., Minchev, I., Steinmetz, M., Monari, G., Laporte, C. F. P., Anders, F., Queiroz, A. B. A., Chiappini, C., Khalatyan, A., Martig, M., McMillan, P., Santiago, B. X., and Youakim, K.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We use Gaia DR2 astrometric and line-of-sight velocity information combined with two sets of distances obtained with a Bayesian inference method to study the 3D velocity distribution in the Milky Way disc. We search for variations in all Galactocentric cylindrical velocity components ($V_{\phi}$, $V_R$ and $V_z$) with Galactic radius, azimuth, and distance from the disc mid-plane. We confirm recent work showing that bulk vertical motions in the $R\text{-}z$ plane are consistent with a combination of breathing and bending modes. In the $x\text{-}y$ plane, we show that, although the amplitudes change, the structure produced by these modes is mostly invariant as a function of distance from the plane. Comparing to two different Galactic disc models, we demonstrate that the observed patterns can drastically change in short time intervals, showing the complexity of understanding the origin of vertical perturbations. A strong radial $V_R$ gradient was identified in the inner disc, transitioning smoothly from $16$ km s$^{-1}$ kpc$^{-1}$ at an azimuth of $30^\circ<\phi<45^\circ$ ahead of the Sun-Galactic centre line, to $-16$ km s$^{-1}$ kpc$^{-1}$ at an azimuth of $-45^\circ<\phi<-30^\circ$ lagging the solar azimuth. We use a simulation with no significant recent mergers to show that exactly the opposite trend is expected from a barred potential, but overestimated distances can flip this trend to match the data. Alternatively, using an $N$-body simulation of the Sagittarius dwarf-Milky Way interaction, we demonstrate that a major recent perturbation is necessary to reproduce the observations. Such an impact may have strongly perturbed the existing bar or even triggered its formation in the last $1\text{-}2$ Gyr., Comment: 17 p., 13 fig., accepted MNRAS

Published
2019
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6. The Pristine survey III: Spectroscopic confirmation of an efficient search for extremely metal-poor stars

Author

Youakim, K., Starkenburg, E., Aguado, D. S., Martin, N. F., Fouesneau, M., Hernández, J. I. González, Prieto, C. Allende, Bonifacio, P., Gentile, M., Kielty, C., Côté, P., Jablonka, P., McConnachie, A., Janssen, R. Sánchez, Tolstoy, E., and Venn, K.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

The Pristine survey is a narrow-band, photometric survey focused around the wavelength region of the Ca II H & K absorption lines, designed to efficiently search for extremely metal-poor stars. In this work, we use the first results of a medium-resolution spectroscopic follow-up to refine the selection criteria for finding extremely metal-poor stars ($\textrm{[Fe/H]} \leq -3.0$) in the Pristine survey. We consider methods by which stars can be selected from available broad-band and infrared photometry plus the additional Pristine narrow-band photometry. The spectroscopic sample presented in this paper consists of 205 stars in the magnitude range $14 < V < 18$. Applying the photometric selection criteria cuts the sample down to 149 stars, and from these we report a success rate of 70% for finding stars with $\textrm{[Fe/H]} \leq -2.5$ and 22% for finding stars with $\textrm{[Fe/H]} \leq -3.0$. These statistics compare favourably with other surveys that search for extremely metal-poor stars, namely an improvement by a factor of $\sim 4-5$ for recovering stars with $\textrm{[Fe/H]} \leq -3.0$. In addition, Pristine covers a fainter magnitude range than its predecessors, and can thus probe deeper into the Galactic halo., Comment: 14 pages, 6 figures, 4 tables, full version of Table 1 available on-line only, accepted for publication in MNRAS

Published
2017
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7. The Pristine survey II: a sample of bright stars observed with FEROS

Author

Caffau, E., Bonifacio, P., Starkenburg, E., Martin, N., Youakim, K., Henden, A. A., Hernandez, J. I. Gonzalez, Aguado, D. S., Prieto, C. Allende, Venn, K., and Jablonka, P.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

Extremely metal-poor (EMP) stars are old objects formed in the first Gyr of the Universe. They are rare and, to select them, the most successful strategy has been to build on large and low-resolution spectroscopic surveys. The combination of narrow- and broad band photometry provides a powerful and cheaper alternative to select metal-poor stars. The on-going Pristine Survey is adopting this strategy, conducting photometry with the CFHT MegaCam wide field imager and a narrow-band filter centred at 395.2 nm on the CaII-H and -K lines. In this paper we present the results of the spectroscopic follow-up conducted on a sample of 26 stars at the bright end of the magnitude range of the Survey (g<=15), using FEROS at the MPG/ESO 2.2 m telescope. From our chemical investigation on the sample, we conclude that this magnitude range is too bright to use the SDSS gri bands, which are typically saturated. Instead the Pristine photometry can be usefully combined with the APASS gri photometry to provide reliable metallicity estimates., Comment: AN accepted

Published
2017
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8. An artificial neural network to discover Hypervelocity stars: Candidates in Gaia DR1/TGAS

Author

Marchetti, T., Rossi, E. M., Kordopatis, G., Brown, A. G. A., Rimoldi, A., Starkenburg, E., Youakim, K., and Ashley, R.

Subjects
Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics
Abstract

The paucity of hypervelocity stars (HVSs) known to date has severely hampered their potential to investigate the stellar population of the Galactic Centre and the Galactic Potential. The first Gaia data release gives an opportunity to increase the current sample. The challenge is the disparity between the expected number of hypervelocity stars and that of bound background stars. We have applied a novel data mining algorithm based on machine learning techniques, an artificial neural network, to the Tycho-Gaia astrometric solution (TGAS) catalogue. With no pre-selection of data, we could exclude immediately $\sim 99 \%$ of the stars in the catalogue and find 80 candidates with more than $90\%$ predicted probability to be HVSs, based only on their position, proper motions, and parallax. We have cross-checked our findings with other spectroscopic surveys, determining radial velocities for 30 and spectroscopic distances for 5 candidates. In addition, follow-up observations have been carried out at the Isaac Newton Telescope for 22 stars, for which we obtained radial velocities and distance estimates. We discover 14 stars with a total velocity in the Galactic rest frame > 400 km/s, and 5 of these have a probability $>50\%$ of being unbound from the Milky Way. Tracing back their orbits in different Galactic potential models we find one possible unbound HVS with velocity $\sim$ 520 km/s, 5 bound HVSs, and, notably, 5 runaway stars with median velocity between 400 and 780 km/s. At the moment, uncertainties in the distance estimates and ages are too large to confirm the nature of our candidates by narrowing down their ejection location, and we wait for future Gaia releases to validate the quality of our sample. This test successfully demonstrates the feasibility of our new data mining routine., Comment: Published in MNRAS, 17 pages, 10 figures

Published
2017
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10. Beyond Gaia DR3: Tracing the [alpla/M] - [M/H] bimodality from the inner to the outer Milky Way disc with Gaia-RVS and convolutional neural networks

Author

Guiglion, G., primary, Nepal, S., additional, Chiappini, C., additional, Khoperskov, S., additional, Traven, G., additional, Queiroz, A.B.A., additional, Steinmetz, M., additional, Valentini, M., additional, Fournier, Y., additional, Vallenari, A., additional, Youakim, K., additional, Bergemann, M., additional, Mészáros, S., additional, Lucatello, S., additional, Sordo, R., additional, Fabbro, S., additional, Minchev, I., additional, Tautvaišiene, G., additional, Mikolaitis, Š., additional, and Montalbán, J., additional

Published
2023
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11. Beyond Gaia DR3: Tracing the [α/M] – [M/H] bimodality from the inner to the outer Milky Way disc with Gaia-RVS and convolutional neural networks.

Author

Guiglion, G., Nepal, S., Chiappini, C., Khoperskov, S., Traven, G., Queiroz, A. B. A., Steinmetz, M., Valentini, M., Fournier, Y., Vallenari, A., Youakim, K., Bergemann, M., Mészáros, S., Lucatello, S., Sordo, R., Fabbro, S., Minchev, I., Tautvaišienė, G., Mikolaitis, Š., and Montalbán, J.

Subjects
CONVOLUTIONAL neural networks, MILKY Way, STARS, STELLAR spectra, MACHINE learning
Abstract

Context. In June 2022, Gaia DR3 provided the astronomy community with about one million spectra from the Radial Velocity Spectrometer (RVS) covering the CaII triplet region. In the next Gaia data releases, we anticipate the number of RVS spectra to successively increase from several 10 million spectra to eventually more than 200 million spectra. Thus, stellar spectra are projected to be produced on an 'industrial scale', with numbers well above those for current and anticipated ground-based surveys. However, one-third of the published spectra have 15 ≤ S /N ≤ 25 per pixel such that they pose problems for classical spectral analysis pipelines, and therefore, alternative ways to tap into these large datasets need to be devised. Aims. We aim to leverage the versatility and capabilities of machine learning techniques for supercharged stellar parametrisation by combining Gaia-RVS spectra with the full set of Gaia products and high-resolution, high-quality ground-based spectroscopic reference datasets. Methods. We developed a hybrid convolutional neural network (CNN) that combines the Gaia DR3 RVS spectra, photometry (G, G_BP, G_RP), parallaxes, and XP coefficients to derive atmospheric parameters (Teff, log(g) as well as overall [M/H]) and chemical abundances ([Fe/H] and [α/M]). We trained the CNN with a high-quality training sample based on APOGEE DR17 labels. Results. With this CNN, we derived homogeneous atmospheric parameters and abundances for 886 080 RVS stars that show remarkable precision and accuracy compared to external datasets (such as GALAH and asteroseismology). The CNN is robust against noise in the RVS data, and we derive very precise labels down to S/N =15. We managed to characterise the [α/M] - [M/H] bimodality from the inner regions to the outer parts of the Milky Way, which has never been done using RVS spectra or similar datasets. Conclusions. This work is the first to combine machine learning with such diverse datasets and paves the way for large-scale machine learning analysis of Gaia-RVS spectra from future data releases. Large, high-quality datasets can be optimally combined thanks to the CNN, thereby realising the full power of spectroscopy, astrometry, and photometry. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Beyond Gaia DR3: tracing the [{\alpha}/M]-[M/H] bimodality from the inner to the outer Milky Way disc with Gaia RVS and Convolutional Neural-Networks

Author

Guiglion, G., Nepal, S., Chiappini, C., Khoperskov, S., Traven, G., Queiroz, A. B. A., Steinmetz, M., Valentini, M., Fournier, Y., Vallenari, A., Youakim, K., Bergemann, M., Mészáros, S., Lucatello, S., Sordo, R., Fabbro, S., Minchev, I., Tautvaišienė, G., Mikolaitis, Š., and Montalbán, J.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

Gaia DR3 has provided the community with about one million RVS spectra covering the CaII triplet region. In the next Gaia data releases, we anticipate the number of RVS spectra to successively increase from several 10 million spectra to eventually more than 200M spectra. Thus, stellar spectra are produced on an "industrial scale" with numbers well above those for current and anticipated ground based surveys. However, many of these spectra have low S/N (from 15 to 25 per pixel), such that they pose problems for classical spectral analysis pipelines and therefore alternative ways to tap into these large datasets need to be devised. We aim to leverage the versatility/capabilities of machine learning techniques for supercharged stellar parametrization, by combining Gaia RVS spectra with the full set of Gaia products and high-resolution, high-quality spectroscopic reference data sets. We develop a hybrid Convolutional Neural-Network (CNN) which combines the Gaia DR3 RVS spectra, photometry (G, Bp, Rp), parallaxes, and XP coefficients to derive atmospheric parameters (Teff, log(g), and overall [M/H]) and chemical abundances ([Fe/H] and [$\alpha$/M]). We trained the CNN with a high-quality training sample based on APOGEE DR17 labels. With this CNN, we derived homogeneous atmospheric parameters and abundances for 841300 stars, that remarkably compared to external data-sets. The CNN is robust against noise in the RVS data, and very precise labels are derived down to S/N=15. We managed to characterize the [$\alpha$/M]-[M/H] bimodality from the inner regions to the outer parts of the Milky Way, which has never been done using RVS spectra or similar datasets. This work is the first to combine machine-learning with such diverse datasets (spectroscopy, astrometry, and photometry), and paves the way for the large scale machine-learning analysis of Gaia-RVS spectra from future data releases., Comment: 24 pages, 24 figures, submitted to A&A

Published
2023

13. Titanium abundances in late-type stars

Author

Mallinson, J. W. E., primary, Lind, K., additional, Amarsi, A. M., additional, Barklem, P. S., additional, Grumer, J., additional, Belyaev, A. K., additional, and Youakim, K., additional

Published
2023
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15. The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

Author

Jin, S, Trager, S, Dalton, G, Aguerri, J, Drew, J, Falcón-Barroso, J, Gänsicke, B, Hill, V, Iovino, A, Pieri, M, Poggianti, B, Smith, D, Vallenari, A, Abrams, D, Aguado, D, Antoja, T, Aragón-Salamanca, A, Ascasibar, Y, Babusiaux, C, Balcells, M, Barrena, R, Battaglia, G, Belokurov, V, Bensby, T, Bonifacio, P, Bragaglia, A, Carrasco, E, Carrera, R, Cornwell, D, Domínguez-Palmero, L, Duncan, K, Famaey, B, Fari na, C, Gonzalez, O, Guest, S, Hatch, N, Hess, K, Hoskin, M, Irwin, M, Knapen, J, Koposov, S, Kuchner, U, Laigle, C, Lewis, J, Longhetti, M, Lucatello, S, Méndez-Abreu, J, Mercurio, A, Molaeinezhad, A, Monguió, M, Morrison, S, Murphy, D, de Arriba, L, Pérez, I, Pérez-Ràfols, I, Picó, S, Raddi, R, Romero-Gómez, M, Royer, F, Siebert, A, Seabroke, G, Som, D, Terrett, D, Thomas, G, Wesson, R, Worley, C, Alfaro, E, Prieto, C, Alonso-Santiago, J, Amos, N, Ashley, R, Balaguer-Nú nez, L, Balbinot, E, Bellazzini, M, Benn, C, Berlanas, S, Bernard, E, Best, P, Bettoni, D, Bianco, A, Bishop, G, Blomqvist, M, Boeche, C, Bolzonella, M, Bonoli, S, Bosma, A, Britavskiy, N, Busarello, G, Caffau, E, Cantat-Gaudin, T, Castro-Ginard, A, Couto, G, Carbajo-Hijarrubia, J, Carter, D, Casamiquela, L, Conrado, A, Corcho-Caballero, P, Costantin, L, Deason, A, de Burgos, A, De Grandi, S, Di Matteo, P, Domínguez-Gómez, J, Dorda, R, Drake, A, Dutta, R, Erkal, D, Feltzing, S, Ferré-Mateu, A, Feuillet, D, Figueras, F, Fossati, M, Franciosini, E, Frasca, A, Fumagalli, M, Gallazzi, A, García-Benito, R, Fusillo, N, Gebran, M, Gilbert, J, Gledhill, T, Delgado, R, Greimel, R, Guarcello, M, Guerra, J, Gullieuszik, M, Haines, C, Hardcastle, M, Harris, A, Haywood, M, Helmi, A, Hernandez, N, Herrero, A, Hughes, S, Irsic, V, Jablonka, P, Jarvis, M, Jordi, C, Kondapally, R, Kordopatis, G, Krogager, J, Barbera, F, Lam, M, Larsen, S, Lemasle, B, Lewis, I, Lhomé, E, Lind, K, Lodi, M, Longobardi, A, Lonoce, I, Magrini, L, Apellániz, J, Marchal, O, Marco, A, Martin, N, Matsuno, T, Maurogordato, S, Merluzzi, P, Miralda-Escudé, J, Molinari, E, Monari, G, Morelli, L, Mottram, C, Naylor, T, Negueruela, I, Onorbe, J, Pancino, E, Peirani, S, Peletier, R, Pozzetti, L, Rainer, M, Ramos, P, Read, S, Rossi, E, Röttgering, H, Rubi no-Martín, J, Montes, J, Juan, J, Sanna, N, Schallig, E, Schiavon, R, Schultheis, M, Serra, P, Shimwell, T, Simón-Díaz, S, Smith, R, Sordo, R, Sorini, D, Soubiran, C, Starkenburg, E, Steele, I, Stott, J, Stuik, R, Tolstoy, E, Tortora, C, Tsantaki, M, Van der Swaelmen, M, van Weeren, R, Vergani, D, Verheijen, M, Verro, K, Vink, J, Vioque, M, Walcher, C, Walton, N, Wegg, C, Weijmans, A, Williams, W, Wilson, A, Wright, N, Xylakis-Dornbusch, T, Youakim, K, Zibetti, S, Zurita, C, Jin, Shoko, Trager, Scott C, Dalton, Gavin B, Aguerri, J Alfonso L, Drew, J E, Falcón-Barroso, Jesús, Gänsicke, Boris T, Hill, Vanessa, Iovino, Angela, Pieri, Matthew M, Poggianti, Bianca M, Smith, D J B, Vallenari, Antonella, Abrams, Don Carlos, Aguado, David S, Antoja, Teresa, Aragón-Salamanca, Alfonso, Ascasibar, Yago, Babusiaux, Carine, Balcells, Marc, Battaglia, Giuseppina, Belokurov, Vasily, Bensby, Thomas, Bonifacio, Piercarlo, Bragaglia, Angela, Carrasco, Esperanza, Carrera, Ricardo, Cornwell, Daniel J, Domínguez-Palmero, Lilian, Duncan, Kenneth J, Famaey, Benoit, Fari na, Cecilia, Gonzalez, Oscar A, Guest, Steve, Hatch, Nina A, Hess, Kelley M, Hoskin, Matthew J, Irwin, Mike, Knapen, Johan H, Koposov, Sergey E, Kuchner, Ulrike, Laigle, Clotilde, Lewis, Jim, Longhetti, Marcella, Lucatello, Sara, Méndez-Abreu, Jairo, Mercurio, Amata, Molaeinezhad, Alireza, Monguió, Maria, Morrison, Sean, Murphy, David N A, de Arriba, Luis Peralta, Pérez, Isabel, Pérez-Ràfols, Ignasi, Picó, Sergio, Raddi, Roberto, Romero-Gómez, Mercè, Royer, Frédéric, Siebert, Arnaud, Seabroke, George M, Som, Debopam, Terrett, David, Thomas, Guillaume, Wesson, Roger, Worley, C Clare, Alfaro, Emilio J, Prieto, Carlos Allende, Alonso-Santiago, Javier, Amos, Nicholas J, Ashley, Richard P, Balaguer-Nú nez, Lola, Balbinot, Eduardo, Bellazzini, Michele, Benn, Chris R, Berlanas, Sara R, Bernard, Edouard J, Best, Philip, Bettoni, Daniela, Bianco, Andrea, Bishop, Georgia, Blomqvist, Michael, Boeche, Corrado, Bolzonella, Micol, Bonoli, Silvia, Bosma, Albert, Britavskiy, Nikolay, Busarello, Gianni, Caffau, Elisabetta, Cantat-Gaudin, Tristan, Castro-Ginard, Alfred, Couto, Guilherme, Carbajo-Hijarrubia, Juan, Carter, David, Casamiquela, Laia, Conrado, Ana M, Corcho-Caballero, Pablo, Costantin, Luca, Deason, Alis, de Burgos, Abel, De Grandi, Sabrina, Di Matteo, Paola, Domínguez-Gómez, Jesús, Dorda, Ricardo, Drake, Alyssa, Dutta, Rajeshwari, Erkal, Denis, Feltzing, Sofia, Ferré-Mateu, Anna, Feuillet, Diane, Figueras, Francesca, Fossati, Matteo, Franciosini, Elena, Frasca, Antonio, Fumagalli, Michele, Gallazzi, Anna, García-Benito, Rubén, Fusillo, Nicola Gentile, Gebran, Marwan, Gilbert, James, Gledhill, T M, Delgado, Rosa M González, Greimel, Robert, Guarcello, Mario Giuseppe, Guerra, Jose, Gullieuszik, Marco, Haines, Christopher P, Hardcastle, Martin J, Harris, Amy, Haywood, Misha, Helmi, Amina, Hernandez, Nauzet, Herrero, Artemio, Hughes, Sarah, Irsic, Vid, Jablonka, Pascale, Jarvis, Matt J, Jordi, Carme, Kondapally, Rohit, Kordopatis, Georges, Krogager, Jens-Kristian, Barbera, Francesco La, Lam, Man I, Larsen, Søren S, Lemasle, Bertrand, Lewis, Ian J, Lhomé, Emilie, Lind, Karin, Lodi, Marcello, Longobardi, Alessia, Lonoce, Ilaria, Magrini, Laura, Apellániz, Jesús Maíz, Marchal, Olivier, Marco, Amparo, Martin, Nicolas F, Matsuno, Tadafumi, Maurogordato, Sophie, Merluzzi, Paola, Miralda-Escudé, Jordi, Molinari, Emilio, Monari, Giacomo, Morelli, Lorenzo, Mottram, Christopher J, Naylor, Tim, Negueruela, Ignacio, Onorbe, Jose, Pancino, Elena, Peirani, Sébastien, Peletier, Reynier F, Pozzetti, Lucia, Rainer, Monica, Ramos, Pau, Read, Shaun C, Rossi, Elena Maria, Röttgering, Huub J A, Rubi no-Martín, Jose Alberto, Montes, Jose Sabater, Juan, José San, Sanna, Nicoletta, Schallig, Ellen, Schiavon, Ricardo P, Schultheis, Mathias, Serra, Paolo, Shimwell, Timothy W, Simón-Díaz, Sergio, Smith, Russell J, Sordo, Rosanna, Sorini, Daniele, Soubiran, Caroline, Starkenburg, Else, Steele, Iain A, Stott, John, Stuik, Remko, Tolstoy, Eline, Tortora, Crescenzo, Tsantaki, Maria, Van der Swaelmen, Mathieu, van Weeren, Reinout J, Vergani, Daniela, Verheijen, Marc A W, Verro, Kristiina, Vink, Jorick S, Vioque, Miguel, Walcher, C Jakob, Walton, Nicholas A, Wegg, Christopher, Weijmans, Anne-Marie, Williams, Wendy L, Wilson, Andrew J, Wright, Nicholas J, Xylakis-Dornbusch, Theodora, Youakim, Kris, Zibetti, Stefano, Zurita, Cristina, Jin, S, Trager, S, Dalton, G, Aguerri, J, Drew, J, Falcón-Barroso, J, Gänsicke, B, Hill, V, Iovino, A, Pieri, M, Poggianti, B, Smith, D, Vallenari, A, Abrams, D, Aguado, D, Antoja, T, Aragón-Salamanca, A, Ascasibar, Y, Babusiaux, C, Balcells, M, Barrena, R, Battaglia, G, Belokurov, V, Bensby, T, Bonifacio, P, Bragaglia, A, Carrasco, E, Carrera, R, Cornwell, D, Domínguez-Palmero, L, Duncan, K, Famaey, B, Fari na, C, Gonzalez, O, Guest, S, Hatch, N, Hess, K, Hoskin, M, Irwin, M, Knapen, J, Koposov, S, Kuchner, U, Laigle, C, Lewis, J, Longhetti, M, Lucatello, S, Méndez-Abreu, J, Mercurio, A, Molaeinezhad, A, Monguió, M, Morrison, S, Murphy, D, de Arriba, L, Pérez, I, Pérez-Ràfols, I, Picó, S, Raddi, R, Romero-Gómez, M, Royer, F, Siebert, A, Seabroke, G, Som, D, Terrett, D, Thomas, G, Wesson, R, Worley, C, Alfaro, E, Prieto, C, Alonso-Santiago, J, Amos, N, Ashley, R, Balaguer-Nú nez, L, Balbinot, E, Bellazzini, M, Benn, C, Berlanas, S, Bernard, E, Best, P, Bettoni, D, Bianco, A, Bishop, G, Blomqvist, M, Boeche, C, Bolzonella, M, Bonoli, S, Bosma, A, Britavskiy, N, Busarello, G, Caffau, E, Cantat-Gaudin, T, Castro-Ginard, A, Couto, G, Carbajo-Hijarrubia, J, Carter, D, Casamiquela, L, Conrado, A, Corcho-Caballero, P, Costantin, L, Deason, A, de Burgos, A, De Grandi, S, Di Matteo, P, Domínguez-Gómez, J, Dorda, R, Drake, A, Dutta, R, Erkal, D, Feltzing, S, Ferré-Mateu, A, Feuillet, D, Figueras, F, Fossati, M, Franciosini, E, Frasca, A, Fumagalli, M, Gallazzi, A, García-Benito, R, Fusillo, N, Gebran, M, Gilbert, J, Gledhill, T, Delgado, R, Greimel, R, Guarcello, M, Guerra, J, Gullieuszik, M, Haines, C, Hardcastle, M, Harris, A, Haywood, M, Helmi, A, Hernandez, N, Herrero, A, Hughes, S, Irsic, V, Jablonka, P, Jarvis, M, Jordi, C, Kondapally, R, Kordopatis, G, Krogager, J, Barbera, F, Lam, M, Larsen, S, Lemasle, B, Lewis, I, Lhomé, E, Lind, K, Lodi, M, Longobardi, A, Lonoce, I, Magrini, L, Apellániz, J, Marchal, O, Marco, A, Martin, N, Matsuno, T, Maurogordato, S, Merluzzi, P, Miralda-Escudé, J, Molinari, E, Monari, G, Morelli, L, Mottram, C, Naylor, T, Negueruela, I, Onorbe, J, Pancino, E, Peirani, S, Peletier, R, Pozzetti, L, Rainer, M, Ramos, P, Read, S, Rossi, E, Röttgering, H, Rubi no-Martín, J, Montes, J, Juan, J, Sanna, N, Schallig, E, Schiavon, R, Schultheis, M, Serra, P, Shimwell, T, Simón-Díaz, S, Smith, R, Sordo, R, Sorini, D, Soubiran, C, Starkenburg, E, Steele, I, Stott, J, Stuik, R, Tolstoy, E, Tortora, C, Tsantaki, M, Van der Swaelmen, M, van Weeren, R, Vergani, D, Verheijen, M, Verro, K, Vink, J, Vioque, M, Walcher, C, Walton, N, Wegg, C, Weijmans, A, Williams, W, Wilson, A, Wright, N, Xylakis-Dornbusch, T, Youakim, K, Zibetti, S, Zurita, C, Jin, Shoko, Trager, Scott C, Dalton, Gavin B, Aguerri, J Alfonso L, Drew, J E, Falcón-Barroso, Jesús, Gänsicke, Boris T, Hill, Vanessa, Iovino, Angela, Pieri, Matthew M, Poggianti, Bianca M, Smith, D J B, Vallenari, Antonella, Abrams, Don Carlos, Aguado, David S, Antoja, Teresa, Aragón-Salamanca, Alfonso, Ascasibar, Yago, Babusiaux, Carine, Balcells, Marc, Battaglia, Giuseppina, Belokurov, Vasily, Bensby, Thomas, Bonifacio, Piercarlo, Bragaglia, Angela, Carrasco, Esperanza, Carrera, Ricardo, Cornwell, Daniel J, Domínguez-Palmero, Lilian, Duncan, Kenneth J, Famaey, Benoit, Fari na, Cecilia, Gonzalez, Oscar A, Guest, Steve, Hatch, Nina A, Hess, Kelley M, Hoskin, Matthew J, Irwin, Mike, Knapen, Johan H, Koposov, Sergey E, Kuchner, Ulrike, Laigle, Clotilde, Lewis, Jim, Longhetti, Marcella, Lucatello, Sara, Méndez-Abreu, Jairo, Mercurio, Amata, Molaeinezhad, Alireza, Monguió, Maria, Morrison, Sean, Murphy, David N A, de Arriba, Luis Peralta, Pérez, Isabel, Pérez-Ràfols, Ignasi, Picó, Sergio, Raddi, Roberto, Romero-Gómez, Mercè, Royer, Frédéric, Siebert, Arnaud, Seabroke, George M, Som, Debopam, Terrett, David, Thomas, Guillaume, Wesson, Roger, Worley, C Clare, Alfaro, Emilio J, Prieto, Carlos Allende, Alonso-Santiago, Javier, Amos, Nicholas J, Ashley, Richard P, Balaguer-Nú nez, Lola, Balbinot, Eduardo, Bellazzini, Michele, Benn, Chris R, Berlanas, Sara R, Bernard, Edouard J, Best, Philip, Bettoni, Daniela, Bianco, Andrea, Bishop, Georgia, Blomqvist, Michael, Boeche, Corrado, Bolzonella, Micol, Bonoli, Silvia, Bosma, Albert, Britavskiy, Nikolay, Busarello, Gianni, Caffau, Elisabetta, Cantat-Gaudin, Tristan, Castro-Ginard, Alfred, Couto, Guilherme, Carbajo-Hijarrubia, Juan, Carter, David, Casamiquela, Laia, Conrado, Ana M, Corcho-Caballero, Pablo, Costantin, Luca, Deason, Alis, de Burgos, Abel, De Grandi, Sabrina, Di Matteo, Paola, Domínguez-Gómez, Jesús, Dorda, Ricardo, Drake, Alyssa, Dutta, Rajeshwari, Erkal, Denis, Feltzing, Sofia, Ferré-Mateu, Anna, Feuillet, Diane, Figueras, Francesca, Fossati, Matteo, Franciosini, Elena, Frasca, Antonio, Fumagalli, Michele, Gallazzi, Anna, García-Benito, Rubén, Fusillo, Nicola Gentile, Gebran, Marwan, Gilbert, James, Gledhill, T M, Delgado, Rosa M González, Greimel, Robert, Guarcello, Mario Giuseppe, Guerra, Jose, Gullieuszik, Marco, Haines, Christopher P, Hardcastle, Martin J, Harris, Amy, Haywood, Misha, Helmi, Amina, Hernandez, Nauzet, Herrero, Artemio, Hughes, Sarah, Irsic, Vid, Jablonka, Pascale, Jarvis, Matt J, Jordi, Carme, Kondapally, Rohit, Kordopatis, Georges, Krogager, Jens-Kristian, Barbera, Francesco La, Lam, Man I, Larsen, Søren S, Lemasle, Bertrand, Lewis, Ian J, Lhomé, Emilie, Lind, Karin, Lodi, Marcello, Longobardi, Alessia, Lonoce, Ilaria, Magrini, Laura, Apellániz, Jesús Maíz, Marchal, Olivier, Marco, Amparo, Martin, Nicolas F, Matsuno, Tadafumi, Maurogordato, Sophie, Merluzzi, Paola, Miralda-Escudé, Jordi, Molinari, Emilio, Monari, Giacomo, Morelli, Lorenzo, Mottram, Christopher J, Naylor, Tim, Negueruela, Ignacio, Onorbe, Jose, Pancino, Elena, Peirani, Sébastien, Peletier, Reynier F, Pozzetti, Lucia, Rainer, Monica, Ramos, Pau, Read, Shaun C, Rossi, Elena Maria, Röttgering, Huub J A, Rubi no-Martín, Jose Alberto, Montes, Jose Sabater, Juan, José San, Sanna, Nicoletta, Schallig, Ellen, Schiavon, Ricardo P, Schultheis, Mathias, Serra, Paolo, Shimwell, Timothy W, Simón-Díaz, Sergio, Smith, Russell J, Sordo, Rosanna, Sorini, Daniele, Soubiran, Caroline, Starkenburg, Else, Steele, Iain A, Stott, John, Stuik, Remko, Tolstoy, Eline, Tortora, Crescenzo, Tsantaki, Maria, Van der Swaelmen, Mathieu, van Weeren, Reinout J, Vergani, Daniela, Verheijen, Marc A W, Verro, Kristiina, Vink, Jorick S, Vioque, Miguel, Walcher, C Jakob, Walton, Nicholas A, Wegg, Christopher, Weijmans, Anne-Marie, Williams, Wendy L, Wilson, Andrew J, Wright, Nicholas J, Xylakis-Dornbusch, Theodora, Youakim, Kris, Zibetti, Stefano, and Zurita, Cristina

Abstract

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable ‘mini’ integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366−959 nm at R ∼ 5000, or two shorter ranges at R ∼ 20 000. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy’s origins by completing Gaia’s phase-space information, providing metallicities to its limiting magnitude for ∼3 million stars and detailed abundances for ∼1.5 million brighter field and open-cluster stars; (ii) survey ∼0.4 million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ∼400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in z < 0.5 cluster galaxies; (vi) survey stellar populations and kinematics in ∼25 000 field galaxies at 0.3 ≲ z ≲ 0.7; (vii) study the cosmic evolution of accretion and star formation using >1 million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at z > 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.

Published
2023

16. Titanium abundances in late-type stars

Author

Mallinson, J. W. E., primary, Lind, K., additional, Amarsi, A. M., additional, Barklem, P. S., additional, Grumer, J., additional, Belyaev, A. K., additional, and Youakim, K., additional

Published
2022
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17. Beyond Gaia DR3: tracing the [α/M]-[M/H] bimodality from the inner to the outer Milky Way disc with Gaia RVS and Convolutional Neural-Networks

Author

Guiglion, G., Nepal, S., Chiappini, C., Khoperskov, S., Traven, G., Queiroz, A. B. A., Steinmetz, M., Valentini, M., Fournier, Y., Vallenari, A., Youakim, K., Bergemann, M., Mészáros, S., Lucatello, S., Sordo, R., Fabbro, S., Minchev, I., Tautvaišienė, G., Mikolaitis, Š., and Montalbán, J.

Subjects
Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences
Abstract

Gaia DR3 has provided the community with about one million RVS spectra covering the CaII triplet region. In the next Gaia data releases, we anticipate the number of RVS spectra to successively increase from several 10 million spectra to eventually more than 200M spectra. Thus, stellar spectra are produced on an "industrial scale" with numbers well above those for current and anticipated ground based surveys. However, many of these spectra have low S/N (from 15 to 25 per pixel), such that they pose problems for classical spectral analysis pipelines and therefore alternative ways to tap into these large datasets need to be devised. We aim to leverage the versatility/capabilities of machine learning techniques for supercharged stellar parametrization, by combining Gaia RVS spectra with the full set of Gaia products and high-resolution, high-quality spectroscopic reference data sets. We develop a hybrid Convolutional Neural-Network (CNN) which combines the Gaia DR3 RVS spectra, photometry (G, Bp, Rp), parallaxes, and XP coefficients to derive atmospheric parameters (Teff, log(g), and overall [M/H]) and chemical abundances ([Fe/H] and [$α$/M]). We trained the CNN with a high-quality training sample based on APOGEE DR17 labels. With this CNN, we derived homogeneous atmospheric parameters and abundances for 841300 stars, that remarkably compared to external data-sets. The CNN is robust against noise in the RVS data, and very precise labels are derived down to S/N=15. We managed to characterize the [$α$/M]-[M/H] bimodality from the inner regions to the outer parts of the Milky Way, which has never been done using RVS spectra or similar datasets. This work is the first to combine machine-learning with such diverse datasets (spectroscopy, astrometry, and photometry), and paves the way for the large scale machine-learning analysis of Gaia-RVS spectra from future data releases., 24 pages, 24 figures, submitted to A&A

Published
2023
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18. Erratum: The Pristine survey – VI: The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates (Monthly Notices of the Royal Astronomical Society (2019) 490 (2241-2253) DOI: 10.1093/mnras/stz2643)

Author

Aguado D. S., Youakim K., Gonzalez Hernandez J. I., Prieto C. A., Starkenburg E., Martin N., Bonifacio P., Arentsen A., Caffau E., Peralta de Arriba L., Sestito F., Garcia-Dias R., Fantin N., Hill V., Jablonca P., Jahandar F., Kielty C., Longeard N., Lucchesi R., Sanchez-Janssen R., Osorio Y., Palicio P. A., Tolstoy E., Wilson T. G., Cote P., Kordopatis G., Lardo C., Navarro J. F., Thomas G. F., Venn K., Aguado D.S., Youakim K., Gonzalez Hernandez J.I., Prieto C.A., Starkenburg E., Martin N., Bonifacio P., Arentsen A., Caffau E., Peralta de Arriba L., Sestito F., Garcia-Dias R., Fantin N., Hill V., Jablonca P., Jahandar F., Kielty C., Longeard N., Lucchesi R., Sanchez-Janssen R., Osorio Y., Palicio P.A., Tolstoy E., Wilson T.G., Cote P., Kordopatis G., Lardo C., Navarro J.F., Thomas G.F., and Venn K.

Subjects
metallicity distribution
Published
2020

19. The Pristine Inner Galaxy Survey (PIGS) I : tracing the kinematics of metal-poor stars in the Galactic bulge

Author

Arentsen, A., Starkenburg, E., Martin, N. F., Hill, V., Ibata, R., Kunder, A., Schultheis, M., Venn, K. A., Zucker, D. B., Aguado, D., Carlberg, R., González Hernández, J., Lardo, C., Longeard, N., Malhan, Khyati, Navarro, J. F., Sánchez-Janssen, R., Sestito, F., Thomas, G., Youakim, K., Lewis, G. F., Simpson, J. D., Wan, Z., Arentsen, A., Starkenburg, E., Martin, N. F., Hill, V., Ibata, R., Kunder, A., Schultheis, M., Venn, K. A., Zucker, D. B., Aguado, D., Carlberg, R., González Hernández, J., Lardo, C., Longeard, N., Malhan, Khyati, Navarro, J. F., Sánchez-Janssen, R., Sestito, F., Thomas, G., Youakim, K., Lewis, G. F., Simpson, J. D., and Wan, Z.

Abstract

Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the importance of a classical, pressure-supported component within the central part of the Milky Way is still being debated. It should be most visible at low metallicity, a regime that has not yet been studied in detail. Using metallicity-sensitive narrow-band photometry, the Pristine Inner Galaxy Survey (PIGS) has collected a large sample of metal-poor ([Fe/H] < -1.0) stars in the inner Galaxy to address this open question. We use PIGS to trace the metal-poor inner Galaxy kinematics as function of metallicity for the first time. We find that the rotational signal decreases with decreasing [Fe/H], until it becomes negligible for the most metal-poor stars. Additionally, the velocity dispersion increases with decreasing metallicity for -3.0 < [Fe/II] < -0.5, with a gradient of -44 +/- 41un s(-1)dex(-1). These observations may signal a transition between Galactic components of different metallicities and kinematics, a different mapping on to the boxy/peanut-shaped bulge for former disc stars of different metallicities and/or the secular dynamical and gravitational influence of the bar on the pressure-supported component. Our results provide strong constraints on models that attempt to explain the properties of the inner Galaxy.

Published
2020
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20. The Pristine Inner Galaxy Survey (PIGS) I: Tracing the kinematics of metal-poor stars in the Galactic bulge

Author

Arentsen, A, Starkenburg, E, Martin, NF, Hill, V, Ibata, R, Kunder, A, Schultheis, M, Venn, KA, Zucker, DB, Aguado, D, Carlberg, R, González Hernández, JI, Lardo, C, Longeard, N, Malhan, K, Navarro, JF, Sánchez-Janssen, R, Sestito, F, Thomas, G, Youakim, K, Lewis, GF, Simpson, JD, Wan, Z, Arentsen, A, Starkenburg, E, Martin, NF, Hill, V, Ibata, R, Kunder, A, Schultheis, M, Venn, KA, Zucker, DB, Aguado, D, Carlberg, R, González Hernández, JI, Lardo, C, Longeard, N, Malhan, K, Navarro, JF, Sánchez-Janssen, R, Sestito, F, Thomas, G, Youakim, K, Lewis, GF, Simpson, JD, and Wan, Z

Abstract

Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the importance of a classical, pressure-supported component within the central part of the Milky Way is still being debated. It should be most visible at low metallicity, a regime that has not yet been studied in detail. Using metallicity-sensitive narrow-band photometry, the Pristine Inner Galaxy Survey (PIGS) has collected a large sample of metal-poor ([Fe/H]<-1.0$) stars in the inner Galaxy to address this open question. We use PIGS to trace the metal-poor inner Galaxy kinematics as function of metallicity for the first time. We find that the rotational signal decreases with decreasing [Fe/H], until it becomes negligible for the most metal-poor stars. Additionally, the velocity dispersion increases with decreasing metallicity for $-3.0<[Fe/H]<-0.5, with a gradient of-44 ± 4 km s-1 dex-1. These observations may signal a transition between Galactic components of different metallicities and kinematics, a different mapping on to the boxy/peanut-shaped bulge for former disc stars of different metallicities and/or the secular dynamical and gravitational influence of the bar on the pressure-supported component. Our results provide strong constraints on models that attempt to explain the properties of the inner Galaxy.

Published
2020

21. The Pristine Survey – VIII. The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime

Author

Youakim, K, primary, Starkenburg, E, additional, Martin, N F, additional, Matijevič, G, additional, Aguado, D S, additional, Allende Prieto, C, additional, Arentsen, A, additional, Bonifacio, P, additional, Carlberg, R G, additional, González Hernández, J I, additional, Hill, V, additional, Kordopatis, G, additional, Lardo, C, additional, Navarro, J F, additional, Jablonka, P, additional, Sánchez Janssen, R, additional, Sestito, F, additional, Thomas, G F, additional, and Venn, K, additional

Published
2020
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22. Hypervelocity star candidates in Gaia DR1/TGAS

Author

Marchetti, T., Rossi, E.M., Kordopatis, G., Brown, A.G.A., Rimoldi, A., Starkenburg, E., Youakim, K., Ashley, R., Recio-Blanco, A., Laverny, P. de, Brown, A., Prusti, T., 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, 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), Recio-Blanco, A., Laverny, P. de, Brown, A., and Prusti, T.

Subjects
Physics, 010504 meteorology & atmospheric sciences, Astronomy, Astronomy and Astrophysics, Astrometry, Star (graph theory), 01 natural sciences, Space and Planetary Science, 0103 physical sciences, Hypervelocity, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

Hypervelocity stars (HVSs) are characterized by a total velocity in excess of the Galactic escape speed, and with trajectories consistent with coming from the Galactic Centre. We apply a novel data mining routine, an artificial neural network, to discover HVSs in the TGAS subset of the first data release of the Gaia satellite, using only the astrometry of the stars. We find 80 stars with a predicted probability >90% of being HVSs, and we retrieved radial velocities for 47 of those. We discover 14 objects with a total velocity in the Galactic rest frame >400 km s−1, and 5 of these have a probability >50% of being unbound from the Milky Way. Tracing back orbits in different Galactic potentials, we discover 1 HVS candidate, 5 bound HVS candidates, and 5 runaway star candidates with remarkably high velocities, between 400 and 780 km s−1. We wait for future Gaia releases to confirm the goodness of our sample and to increase the number of HVS candidates.

Published
2018

23. The Pristine Inner Galaxy Survey (PIGS) I: tracing the kinematics of metal-poor stars in the Galactic bulge

Author

Arentsen, A, primary, Starkenburg, E, additional, Martin, N F, additional, Hill, V, additional, Ibata, R, additional, Kunder, A, additional, Schultheis, M, additional, Venn, K A, additional, Zucker, D B, additional, Aguado, D, additional, Carlberg, R, additional, González Hernández, J I, additional, Lardo, C, additional, Longeard, N, additional, Malhan, K, additional, Navarro, J F, additional, Sánchez-Janssen, R, additional, Sestito, F, additional, Thomas, G, additional, Youakim, K, additional, Lewis, G F, additional, Simpson, J D, additional, and Wan, Z, additional

Published
2019
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24. Kinematics with Gaia DR2: the force of a dwarf

Author

Carrillo, I, primary, Minchev, I, additional, Steinmetz, M, additional, Monari, G, additional, Laporte, C F P, additional, Anders, F, additional, Queiroz, A B A, additional, Chiappini, C, additional, Khalatyan, A, additional, Martig, M, additional, McMillan, P J, additional, Santiago, B X, additional, and Youakim, K, additional

Published
2019
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25. The Pristine survey – III. Spectroscopic confirmation of an efficient search for extremely metal-poor stars

Author

Youakim, K., primary, Starkenburg, E., additional, Aguado, D. S., additional, Martin, N. F., additional, Fouesneau, M., additional, González Hernández, J. I., additional, Allende Prieto, C., additional, Bonifacio, P., additional, Gentile, M., additional, Kielty, C., additional, Côté, P., additional, Jablonka, P., additional, McConnachie, A., additional, Sánchez Janssen, R., additional, Tolstoy, E., additional, and Venn, K., additional

Published
2017
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26. The Pristine survey II: A sample of bright stars observed with FEROS

Author

Caffau, E., primary, Bonifacio, P., additional, Starkenburg, E., additional, Martin, N., additional, Youakim, K., additional, Henden, A. A., additional, González Hernández, J. I., additional, Aguado, D. S., additional, Prieto, C. Allende, additional, Venn, K., additional, and Jablonka, P., additional

Published
2017
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28. Hypervelocity star candidates in Gaia DR1/TGAS

Author

Marchetti, T., primary, Rossi, E. M., additional, Kordopatis, G., additional, Brown, A. G. A., additional, Rimoldi, A., additional, Starkenburg, E., additional, Youakim, K., additional, and Ashley, R., additional

Published
2017
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29. Using the multi-object adaptive optics demonstrator RAVEN to observe metal-poor stars in and towards the Galactic Centre

Author

Lamb, M., primary, Venn, K., additional, Andersen, D., additional, Oya, S., additional, Shetrone, M., additional, Fattahi, A., additional, Howes, L., additional, Asplund, M., additional, Lardière, O., additional, Akiyama, M., additional, Ono, Y., additional, Terada, H., additional, Hayano, Y., additional, Suzuki, G., additional, Blain, C., additional, Jackson, K., additional, Correia, C., additional, Youakim, K., additional, and Bradley, C., additional

Published
2016
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30. Using the multi-object adaptive optics demonstrator RAVEN to observe metal-poor stars in and towards the Galactic Centre.

Author

Lamb, M., Venn, K., Andersen, D., Oya, S., Shetrone, M., Fattahi, A., Howes, L., Asplund, M., Lardière, O., Akiyama, M., Ono, Y., Terada, H., Hayano, Y., Suzuki, G., Blain, C., Jackson, K., Correia, C., Youakim, K., and Bradley, C.

Subjects
METAL-poor stars, STAR observations, ADAPTIVE optics, GALACTIC center, COSMIC abundances, INFRARED spectroscopy
Abstract

The chemical abundances for five metal-poor stars in and towards the Galactic bulge have been determined from the H-band infrared spectroscopy taken with the RAVEN multi-object adaptive optics science demonstrator and the Infrared Camera and Spectrograph at the Subaru 8.2-m telescope. Three of these stars are in the Galactic bulge and have metallicities between -2.1<[Fe/H]<-1.5, and high [α/Fe]~+0.3, typical of Galactic disc and bulge stars in this metallicity range; [Al/Fe] and [N/Fe] are also high, whereas [C/Fe] < +0.3. An examination of their orbits suggests that two of these stars may be confined to the Galactic bulge and one is a halo trespasser, though proper motion values used to calculate orbits are quite uncertain. An additional two stars in the globular cluster M22 show [Fe/H] values consistent to within 1σ, although one of these two stars has [Fe/H] = -2.01 ± 0.09, which is on the low end for this cluster. The [α/Fe] and [Ni/Fe] values differ by 2σ, with the most metal-poor star showing significantly higher values for these elements. M22 is known to show element abundance variations, consistent with a multipopulation scenario though our results cannot discriminate this clearly given our abundance uncertainties. This is the first science demonstration of multiobject adaptive optics with high-resolution infrared spectroscopy, and we also discuss the feasibility of this technique for use in the upcoming era of 30-m class telescope facilities. [ABSTRACT FROM AUTHOR]

Published
2017
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31. The Pristine survey IV: approaching the Galactic metallicity floor with the discovery of an ultra-metal-poor star

Author

Piercarlo Bonifacio, D. S. Aguado, A. Arentsen, Eline Tolstoy, Rubén Sánchez-Janssen, Patrick Côté, Elisabetta Caffau, Kim A. Venn, Vanessa Hill, Julio F. Navarro, Nicolas Longeard, Carlos Allende Prieto, Morgan Fouesneau, Pascale Jablonka, Raymond G. Carlberg, Marc Gentile, Federico Sestito, Else Starkenburg, Collin Kielty, Helmer H. Koppelman, Jonay I. González Hernández, Nicolas F. Martin, Kris Youakim, Carmela Lardo, Alan W. McConnachie, Astronomy, Starkenburg E., Aguado D.S., Bonifacio P., Caffau E., Jablonka P., Lardo C., Martin N., Sanchez-Janssen R., Sestito F., Venn K.A., Youakim K., Prieto C.A., Arentsen A., Gentile M., Hernandez J.I.G., Kielty C., Koppelman H.H., Longeard N., Tolstoy E., Carlberg R.G., Cote P., Fouesneau M., Hill V., McConnachie A.W., Navarro J.F., Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (UMR 6174) (FEMTO-ST), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS), National Research Council of Canada (NRC), 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), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, 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, and 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)

Subjects
photometry, stars: abundances, Metallicity, media_common.quotation_subject, 1st stars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, telescope, Star (graph theory), 01 natural sciences, Galactic halo, Metal, hamburg/eso survey, 0103 physical sciences, Galaxy formation and evolution, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, media_common, [PHYS]Physics [physics], Physics, Galaxy: evolution, abundance, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, stars: abundances, Galaxy: abundances, Galaxy: evolution, Galaxy: formation, Galaxy: halo, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies, model atmospheres, Astrophysics - Astrophysics of Galaxies, chemical-compositions, Universe, sky survey, Galaxy: halo, Galaxy: abundance, Stars, Astrophysics - Solar and Stellar Astrophysics, lithium, 13. Climate action, Space and Planetary Science, Galaxy: formation, Astrophysics of Galaxies (astro-ph.GA), visual_art, visual_art.visual_art_medium, Galaxy: abundances, Astrophysics::Earth and Planetary Astrophysics, halo-stars
Abstract

The early Universe presented a star formation environment that was almost devoid of heavy elements. The lowest metallicity stars thus provide a unique window into the earliest Galactic stages, but are exceedingly rare and difficult to find. Here we present the discovery of an ultra-metal-poor star, Pristine_221.8781+9.7844, using narrow-band Ca H&K photometry from the Pristine survey. Follow-up medium and high-resolution spectroscopy confirms the ultra-metal-poor nature of Pristine_221.8781+9.7844 ([Fe/H] = -4.66 +/- 0.13 in 1D LTE) with an enhancement of 0.3-0.4 dex in alpha-elements relative to Fe, and an unusually low carbon abundance. We derive an upper limit of A(C) = 5.6, well below typical A(C) values for such ultra metal-poor stars. This makes Pristine_221.8781+9.7844 one of the most metal-poor stars; in fact, it is very similar to the most metal-poor star known (SDSS J102915+172927). The existence of a class of ultra metal-poor stars with low(er) carbon abundances suggest that there must have been several formation channels in the early Universe through which long-lived, low-mass stars were formed., Re-submitted to MNRAS after minor revisions

Published
2018

32. The Pristine survey – IX. CFHT ESPaDOnS spectroscopic analysis of 115 bright metal-poor candidate stars

Author

Carmela Lardo, Christopher Sneden, Nicolas F. Martin, Else Starkenburg, Federico Sestito, Julio F. Navarro, Rubén Sánchez Janssen, Jonay I. Gonzalez-Hernandez, Collin Kielty, Pascale Jablonka, Anke Arentsen, K. Youakim, Raymond G. Carlberg, Lyudmilla Mashonkina, Piercarlo Bonifacio, Kim A. Venn, Vanessa Hill, G. F. Thomas, Elisabetta Caffau, David Aguado, Khyati Malhan, Department of Physics and Astronomy [Victoria], University of Victoria [Canada] (UVIC), 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), Leibniz Institute for Astrophysics Potsdam (AIP), Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), 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)-Centre National de la Recherche Scientifique (CNRS), 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), EPFL Laboratoire d’astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Astronomy of the Russian Academy of Sciences (INASAN), Russian Academy of Sciences [Moscow] (RAS), Department of Astronomy [Austin], University of Texas at Austin [Austin], National Research Council Herzberg Astronomy and Astrophysics, Instituto de Astrofisica de Canarias (IAC), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), UK Astronomy Technology Centre (UK ATC), Science and Technology Facilities Council (STFC), Department of Astronomy and Astrophysics [Universty of Toronto], University of Toronto, The Oskar Klein Centre for Cosmoparticle Physics and Department of Physics, Stockholm University, Venn K.A., Kielty C.L., Sestito F., Starkenburg E., Martin N., Aguado D.S., Arentsen A., Bonifacio P., Caffau E., Hill V., Jablonka P., Lardo C., Mashonkina L., Navarro J.F., Sneden C., Thomas G., Youakim K., Gonzalez-Hernandez J.I., Janssen R.S., Carlberg R., Malhan K., University of British Columbia (UBC), Institute of Astronomy, University of Cambridge, 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), Centre National de la Recherche Scientifique (CNRS)-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)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA), and Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France.

Subjects
Star, stars: abundances, Milky Way, stars: kinematics and dynamics, 1st stars, Stellar content -Galaxy, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, fe, lte line formation, hamburg/eso survey, Abundance, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, Spectroscopy, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, milky-way, Astrophysics::Galaxy Astrophysics, Population II, Physics, stellar halo, [PHYS]Physics [physics], Galaxy: stellar content, galactic bar, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Galactic Center, Astronomy and Astrophysics, stars: Population II, Kinematics and dynamic, model atmospheres, Galaxy, Stars, Narrow band, Hamburg/ESO Survey, 13. Climate action, Space and Planetary Science, Galaxy: abundances, chemical-composition, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Galaxy: kinematics and dynamics
Abstract

A chemo-dynamical analysis of 115 metal-poor candidate stars selected from the narrow-band Pristine photometric survey is presented based on CFHT high-resolution ESPaDOnS spectroscopy. We have discovered 28 new bright (V < 15) stars with [Fe/H] < −2.5 and 5 with [Fe/H] < −3.0 for success rates of 40 (28/70) and 19 per cent (5/27), respectively. A detailed model atmosphere analysis is carried out for the 28 new metal-poor stars. Stellar parameters were determined from SDSS photometric colours, Gaia DR2 parallaxes, MESA/MIST stellar isochrones, and the initial Pristine survey metallicities, following a Bayesian inference method. Chemical abundances are determined for 10 elements (Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Y, and Ba). Most stars show chemical abundance patterns that are similar to the normal metal-poor stars in the Galactic halo; however, we also report the discoveries of a new r-process-rich star, a new CEMP-s candidate with [Y/Ba] > 0, and a metal-poor star with very low [Mg/Fe]. The kinematics and orbits for all of the highly probable metal-poor candidates are determined by combining our precision radial velocities with Gaia DR2 proper motions. Some stars show unusual kinematics for their chemistries, including planar orbits, unbound orbits, and highly elliptical orbits that plunge deeply into the Galactic bulge (Rperi < 0.5 kpc); also, eight stars have orbital energies and actions consistent with the Gaia-Enceladus accretion event. This paper contributes to our understanding of the complex chemo-dynamics of the metal-poor Galaxy, and increases the number of known bright metal-poor stars available for detailed nucleosynthetic studies.

Published
2020

33. The Pristine survey VIII: The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime

Author

G. F. Thomas, Vanessa Hill, Julio F. Navarro, Else Starkenburg, Nicolas F. Martin, Anke Arentsen, Georges Kordopatis, J. I. González Hernández, R. Sánchez Janssen, K. Youakim, C. Allende Prieto, David Aguado, K. A. Venn, Pascale Jablonka, Carmela Lardo, R. G. Carlberg, Federico Sestito, Gal Matijevic, Piercarlo Bonifacio, Youakim, K., Starkenburg, E., Martin, N. F., Matijevič, G., Aguado, D. S., Allende Prieto, C., Arentsen, A., Bonifacio, P., Carlberg, R. G., González Hernández, J. I., Hill, V., Kordopatis, G., Lardo, C., Navarro, J. F., Jablonka, P., Sánchez Janssen, R., Sestito, F., Thomas, G. F., Venn, K., 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), 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)-Centre National de la Recherche Scientifique (CNRS), University of Toronto, 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), Ecole Polytechnique Fédérale de Lausanne (EPFL), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)

Subjects
stars, stars: abundances, Metallciity, galaxy: evolution, Metallicity, Milky Way, FOS: Physical sciences, dwarf galaxy, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, galaxy: formation, Photometry (optics), Galactic halo, galaxy: halo, evolution, 0103 physical sciences, Galaxy formation and evolution, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, merger, [PHYS]Physics [physics], stellar halo, search, Physics, abundance, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], galaxy: abundances, 010308 nuclear & particles physics, sagittarius, Near-field cosmology, Astronomy and Astrophysics, galaxies: dwarf, Metal-poor star, streams, Astrophysics - Astrophysics of Galaxies, sky survey, Stars, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Globular cluster, Halo, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ([Fe/H] < -3), and currently consists of over 4 million FGK-type stars over a sky area of $\sim 2~500\, \mathrm{deg}^2$. We focus our analysis on a subsample of $\sim 80~000$ main sequence turnoff stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at [Fe/H] = -1.6, and a slope of $��$(LogN)/$��[Fe/H] = 1.0 \pm 0.1$ in the metallicity range of -3.4 < [Fe/H] < -2.5. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low latitude field in the anticenter direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for [Fe/H] < -2.5 and 1.5 for [Fe/H] < -3, suggesting that the lack of low metallicity globular clusters in the Milky Way is not due simply to statistical undersampling., 17 pages, 12 figures, 5 tables, accepted for publication in MNRAS

Published
2020

34. The Pristine Inner Galaxy Survey (PIGS) I: Tracing the kinematics of metal-poor stars in the Galactic bulge

Author

Mathias Schultheis, Jeffrey D. Simpson, Zhen Wan, Anke Arentsen, G. F. Thomas, Nicolas F. Martin, K. A. Venn, Rodrigo A. Ibata, K. Youakim, Daniel B. Zucker, Nicolas Longeard, J. I. González Hernández, Vanessa Hill, Julio F. Navarro, Andrea Kunder, R. G. Carlberg, Carmela Lardo, Khyati Malhan, Geraint F. Lewis, Rubén Sánchez-Janssen, David Aguado, Federico Sestito, Else Starkenburg, Arentsen A., Starkenburg E., Martin N.F., Hill V., Ibata R., Kunder A., Schultheis M., Venn K.A., Zucker D.B., Aguado D., Carlberg R., Gonzalez Hernandez J.I., Lardo C., Longeard N., Malhan K., Navarro J.F., Sanchez-Janssen R., Sestito F., Thomas G., Youakim K., Lewis G.F., Simpson J.D., Wan Z., Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France., Centre International de Hautes Etudes Agronomiques Méditerranéennes - Institut Agronomique Méditerranéen de Montpellier (CIHEAM-IAMM), Centre International de Hautes Études Agronomiques Méditerranéennes (CIHEAM), Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 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, 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), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Toronto, Ecole Polytechnique Fédérale de Lausanne (EPFL), Facultad de Matematicas, Universidad de Murcia, CLRC Daresbury, SFTC, 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), Centre National de la Recherche Scientifique (CNRS)-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)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), and COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)

Subjects
photometry, Milky Way, Metallicity, bulge -Galaxy, kinematics and dynamics -Galaxy, formation -Galaxy, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Galaxy: Structure, Galactic halo, Galaxy: Evolution, Bulge, 0103 physical sciences, Galaxy formation and evolution, structure, 010303 astronomy & astrophysics, Galaxy: Halo, halo -Galaxy, milky-way, ComputingMilieux_MISCELLANEOUS, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Galaxy: Kinematics and dynamic, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stellar populations, Velocity dispersion, Astronomy and Astrophysics, Galaxy: Formation, argos, Galaxy: Bulge, Astrophysics - Astrophysics of Galaxies, Galaxy, evolution -Galaxy, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Stars, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxy: kinematics and dynamics, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the importance of a classical, pressure-supported component within the central part of the Milky Way is still being debated. It should be most visible at low metallicity, a regime that has not yet been studied in detail. Using metallicity-sensitive narrow-band photometry, the Pristine Inner Galaxy Survey (PIGS) has collected a large sample of metal-poor ([Fe/H] < -1.0) stars in the inner Galaxy to address this open question. We use PIGS to trace the metal-poor inner Galaxy kinematics as function of metallicity for the first time. We find that the rotational signal decreases with decreasing [Fe/H], until it becomes negligible for the most metal-poor stars. Additionally, the velocity dispersion increases with decreasing metallicity for -3.0 < [Fe/H] < -0.5, with a gradient of -44 $\pm$ 4 km$\,$s$^{-1}\,$dex$^{-1}$. These observations may signal a transition between Galactic components of different metallicities and kinematics, a different mapping onto the boxy/peanut-shaped bulge for former disk stars of different metallicities and/or the secular dynamical and gravitational influence of the bar on the pressure-supported component. Our results provide strong constraints on models that attempt to explain the properties of the inner Galaxy., 5 pages + appendices, accepted to MNRAS Letters

Published
2020

35. The Pristine survey VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates

Author

Carmela Lardo, K. Youakim, Nicolas F. Martin, Rafael Garcia-Dias, Thomas G. Wilson, Luis Peralta de Arriba, Julio F. Navarro, Vanessa Hill, Pascale Jablonca, Pedro A. Palicio, Georges Kordopatis, Nicholas J. Fantin, Federico Sestito, Carlos Allende Prieto, Else Starkenburg, R. Lucchesi, Jonay I. González Hernández, Yeisson Osorio, Farbod Jahandar, Kim A. Venn, Rubén Sánchez-Janssen, David Aguado, Nicolas Longeard, Anke Arentsen, Collin Kielty, Elisabetta Caffau, Guillaume F. Thomas, Patrick Côté, Eline Tolstoy, Piercarlo Bonifacio, Institute of Astronomy, University of Cambridge, Universidad de La Laguna [Tenerife - SP] (ULL), Leibniz Institute for Astrophysics Potsdam (AIP), 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), Cosmological Impact of the First Stars (CIFIST), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), 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)-Centre National de la Recherche Scientifique (CNRS), Peralta de Arriba, Luis [0000-0002-3084-084X], Apollo - University of Cambridge Repository, Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astronomy, Aguado D.S., Youakim K., Gonzalez Hernandez J.I., Prieto C.A., Starkenburg E., Martin N., Bonifacio P., Arentsen A., Caffau E., de Arriba L.P., Sestito F., Garcia-Dias R., Fantin N., Hill V., Jablonca P., Jahandar F., Kielty C., Longeard N., Lucchesi R., Sanchez-Janssen R., Osorio Y., Palicio P.A., Tolstoy E., Wilson T.G., Cote P., Kordopatis G., Lardo C., Navarro J.F., Thomas G.F., and Venn K.

Subjects
stars: abundances, galaxy: evolution, Milky Way, first stars, Dark age, halo, FOS: Physical sciences, Astrophysics, 01 natural sciences, local group, galaxy: formation, First star, 0103 physical sciences, evolution, Galaxy formation and evolution, William Herschel Telescope, dark ages, reionization, first stars, metal-poor stars, dark ages, Spectroscopy, 010303 astronomy & astrophysics, Reionization, ComputingMilieux_MISCELLANEOUS, milky-way, Physics, [PHYS]Physics [physics], search, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, abundances, carbon, Astronomy and Astrophysics, oldest, Astrophysics - Astrophysics of Galaxies, early universe, Medium resolution, Stars, classification, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), reionization, discovery
Abstract

We present the results of a 3-year long, medium-resolution spectroscopic campaign aimed at identifying very metal-poor stars from candidates selected with the CaHK, metallicity-sensitive Pristine survey. The catalogue consists of a total of 1007 stars, and includes 146 rediscoveries of metal-poor stars already presented in previous surveys, 707 new very metal-poor stars with [Fe/H] < -2.0, and 95 new extremely metal-poor stars with [Fe/H] < -3.0. We provide a spectroscopic [Fe/H] for every star in the catalogue, and [C/Fe] measurements for a subset of the stars (10% with [Fe/H] < -3 and 24% with -3 < [Fe/H] < -2) for which a carbon determination is possible, contingent mainly on the carbon abundance, effective temperature and S/N of the stellar spectra. We find an average carbon enhancement fraction ([C/Fe] >= +0.7) of 41 +- 4% for stars with -3 < [Fe/H] < -2 and 58 +- 14% for stars with [Fe/H] < -3, and report updated success rates for the Pristine survey of 56 % and 23 % to recover stars with [Fe/H] < -2.5 and [Fe/H] < -3, respectively. Finally, we discuss the current status of the survey and its preparation for providing targets to upcoming multi-object spectroscopic surveys such as WEAVE., 13 pages 6 figures, accepted for publication in MNRAS

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