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1. Signatures of simulated spiral arms on radial actions

Author

Palicio, P. A., Recio-Blanco, A., Tepper-Garcia, T., Poggio, E., Peirani, S., Dubois, Y., McMillan, P. J., Bland-Hawthorn, J., Kraljic, K., and Barbillon, M.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

Among the various implications of the spiral arms, it has been observed in the Milky Way disc that the distribution of radial actions from the Gaia Data Release 3 exhibits structures that may be related to the spiral arms. Our goal is to investigate the relationship between regions of low radial action identified in simulated discs and the location of the spiral arms, such as that suggested in Palicio et al. (2023) for the Galaxy. For a sample of 23 simulated spiral galaxies, we modelled the axisymmetric component of their gravitational potential to compute the radial action of their stellar particles using the St\"ackel fudge. The spatial distribution of the radial action was then compared to the location of the spiral arms, identified as overdensities in the stellar surface density using a kernel density estimator. Our analysis reveals a strong correlation between the radial action distribution and the spiral arms in 18 of 23 simulated galaxies. However, notable discrepancies are observed in the remaining five, since they are profoundly out-of-equilibrium systems, such as galaxies influenced by external interactions or spiral arms still in the process of winding up. We have confirmed that, in general, there is a tendency of spatial correlation between spiral arms and stellar populations featuring low values of the radial action observed in Gaia DR3 data by Palicio et al. (2023). However, discrepancies between features in the radial action distribution and the spiral structure can be interpreted as signatures of recent disturbances, a scenario applicable to the Milky Way. Furthermore, populations at least as old as 3 Gyr trace the spiral arms with no significant misalignment across age bins. A linear relation between the maximum value of the radial action of the spiral arms and the vertical scale-length is found, which is also satisfied by the Milky Way., Comment: 25 pages, 18 figures

Published
2024

2. Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry

Author

Gaia Collaboration, Panuzzo, P., Mazeh, T., Arenou, F., Holl, B., Caffau, E., Jorissen, A., Babusiaux, C., Gavras, P., Sahlmann, J., Bastian, U., Wyrzykowski, Ł., Eyer, L., Leclerc, N., Bauchet, N., Bombrun, A., Mowlavi, N., Seabroke, G. M., Teyssier, D., Balbinot, E., Helmi, A., Brown, A. G. A., Vallenari, A., Prusti, T., de Bruijne, J. H. J., Barbier, A., Biermann, M., Creevey, O. L., Ducourant, C., Evans, D. W., Guerra, R., Hutton, A., Jordi, C., Klioner, S. A., Lammers, U., Lindegren, L., Luri, X., Mignard, F., Nicolas, C., Randich, S., Sartoretti, P., Smiljanic, R., Tanga, P., Walton, N. A., Aerts, C., Bailer-Jones, C. A. L., Cropper, M., Drimmel, R., Jansen, F., Katz, D., Lattanzi, M. G., Soubiran, C., Thévenin, F., van Leeuwen, F., Andrae, R., Audard, M., Bakker, J., Blomme, R., Castañeda, J., De Angeli, F., Fabricius, C., Fouesneau, M., Frémat, Y., Galluccio, L., Guerrier, A., Heiter, U., Masana, E., Messineo, R., Nienartowicz, K., Pailler, F., Riclet, F., Roux, W., Sordo, R., Gracia-Abril, G., Portell, J., Altmann, M., Benson, K., Berthier, J., Burgess, P. W., Busonero, D., Busso, G., Cacciari, C., Cánovas, H., Carrasco, J. M., Carry, B., Cellino, A., Cheek, N., Clementini, G., Damerdji, Y., Davidson, M., de Teodoro, P., Delchambre, L., Dell'Oro, A., Garcia, E. Fraile, Garabato, D., García-Lario, P., Haigron, R., Hambly, N. C., Harrison, D. L., Hatzidimitriou, D., Hernández, J., Hestroffer, D., Hodgkin, S. T., Jamal, S., de Fombelle, G. Jevardat, Jordan, S., Krone-Martins, A., Lanzafame, A. C., Löffler, W., Lorca, A., Marchal, O., Marrese, P. M., Moitinho, A., Muinonen, K., Campos, M. Nuñez, Oreshina-Slezak, I., Osborne, P., Pancino, E., Pauwels, T., Recio-Blanco, A., Riello, M., Rimoldini, L., Robin, A. C., Roegiers, T., Sarro, L. M., Schultheis, M., Smith, M., Sozzetti, A., Utrilla, E., van Leeuwen, M., Weingrill, K., Abbas, U., Ábrahám, P., Aramburu, A. Abreu, Ahmed, S., Altavilla, G., Álvarez, M. A., Anders, F., Anderson, R. I., Varela, E. Anglada, Antoja, T., Baig, S., Baines, D., Baker, S. G., Balaguer-Núñez, L., Balog, Z., Barache, C., Barros, M., Barstow, M. A., Bartolomé, S., Bashi, D., Bassilana, J. -L., Baudeau, N., Becciani, U., Bedin, L. R., Bellas-Velidis, I., Bellazzini, M., Beordo, W., Bernet, M., Bertolotto, C., Bertone, S., Bianchi, L., Binnenfeld, A., Blanco-Cuaresma, S., Bland-Hawthorn, J., Blazere, A., Boch, T., Bossini, D., Bouquillon, S., Bragaglia, A., Braine, J., Bratsolis, E., Breedt, E., Bressan, A., Brouillet, N., Brugaletta, E., Bucciarelli, B., Butkevich, A. G., Buzzi, R., Camut, A., Cancelliere, R., Cantat-Gaudin, T., Guilarte, D. Capilla, Carballo, R., Carlucci, T., Carnerero, M. I., Carretero, J., Carton, S., Casamiquela, L., Casey, A., Castellani, M., Castro-Ginard, A., Ceraj, L., Cesare, V., Charlot, P., Chaudet, C., Chemin, L., Chiavassa, A., Chornay, N., Chosson, D., Cooper, W. J., Cornez, T., Cowell, S., Crosta, M., Crowley, C., Reyes, M. Cruz, Dafonte, C., Ponte, M. Dal, David, M., de Laverny, P., De Luise, F., De March, R., De Ridder, J., de Torres, A., del Peloso, E. F., Delbo, M., Delgado, A., Delisle, J. -B., Demouchy, C., Denis, E., Dharmawardena, T. E., Di Giacomo, F., Diener, C., Distefano, E., Dolding, C., Dsilva, K., Enke, H., Fabre, C., Fabrizio, M., Faigler, S., Fatović, M., Fedorets, G., Fernández-Hernández, J., Fernique, P., Figueras, F., Fouron, C., Fragkoudi, F., Gai, M., Galinier, M., Garcia-Serrano, A., García-Torres, M., Garofalo, A., Gerlach, E., Geyer, R., Giacobbe, P., Gilmore, G., Girona, S., Giuffrida, G., Gomboc, A., Gomez, A., González-Santamaría, I., Gosset, E., Granvik, M., Barrera, V. Gregori, Gutiérrez-Sánchez, R., Haywood, M., Helmer, A., Hidalgo, S. L., Hilger, T., Hobbs, D., Hottier, C., Huckle, H. E., Jiménez-Arranz, Ó., Campillo, J. Juaristi, Kaczmarek, Z., Kervella, P., Khanna, S., Kontizas, M., Kordopatis, G., Korn, A. J., Kóspál, Á, Kostrzewa-Rutkowska, Z., Kruszyńska, K., Kun, M., Lambert, S., Lanza, A. F., Lebreton, Y., Lebzelter, T., Leccia, S., Lecoutre, G., Liao, S., Liberato, L., Licata, E., Livanou, E., Lobel, A., López-Miralles, J., Loup, C., Madarász, M., Mahy, L., Mann, R. G., Manteiga, M., Marinoni, S., Marcellino, C. P., Marshall, D. J., Mascarenhas, D., Marchant, J. M., Lozano, J. Martín, Masip, A., Marconi, M., Pina, D. Marín, Polo, L. Martin, Martín-Fleitas, J. M., Mastrobuono-Battisti, A., McMillan, P. J., Meichsner, J. G. Marton, Merc, J., Messina, S., Millar, N. R., Mints, A., Mohamed, D., Molina, D., Molinaro, R., Monguió, M., Montegriffo, P., Monti, L., Mora, A., Morbidelli, R., Morris, D., Mudimadugula, R., Muraveva, T., Musella, I., Nagy, Z., Nardetto, N., Navarrete, C., Oh, S., Ordenovic, C., Orenstein, O., Pagani, C., Pagano, I., Palaversa, L., Palicio, P. A., Pallas-Quintela, L., Pawlak, M., Penttilä, A., Pesciullesi, P., Pinamonti, M., Plachy, E., Planquart, L., Plum, G., Poggio, E., Pourbaix, D., Price-Whelan, A. M., Pulone, L., Rabin, V., Rainer, M., Raiteri, C. M., Ramos, P., Ramos-Lerate, M., Ratajczak, M., Fiorentin, P. Re, Regibo, S., Reylé, C., Ripepi, V., Riva, A., Rix, H. -W., Rixon, G., Robert, G., Robichon, N., Robin, C., Romero-Gómez, M., Rowell, N., Mieres, D. Ruz, Rybicki, K. A., Sadowski, G., Sellés, A. Sagristà, Sanna, N., Santoveña, R., Sarasso, M., Sarmiento, M. H., Riera, C. Sarrate, Sciacca, E., Ségransan, D., Semczuk, M., Shahaf, S., Siebert, A., Slezak18, E., Smart, R. L., Snaith, O. N., Solano, E., Solitro, F., Souami, D., Souchay, J., Spitoni, E., Spoto, F., Squillante, L. A., Steele, I. A., Steidelmüller, H., Surdej, J., Szabados, L., Taris, F., Taylor, M. B., Teixeira, R., Tepper-Garcia, T., Thuillot, W., Tolomei, L., Tonello, N., Torra, F., Elipe, G. Torralba, Trabucchi, M., Trentin, E., Tsantaki, M., Turon, C., Ulla, A., Unger, N., Valtchanov, I., Vanel, O., Vecchiato, A., Vicente, D., Villar, E., Weiler, M., Zhao, H., Zorec, J., Zucker, S., Župić, A., and Zwitter, T.

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

Gravitational waves from black-hole merging events have revealed a population of extra-galactic BHs residing in short-period binaries with masses that are higher than expected based on most stellar evolution models - and also higher than known stellar-origin black holes in our Galaxy. It has been proposed that those high-mass BHs are the remnants of massive metal-poor stars. Gaia astrometry is expected to uncover many Galactic wide-binary systems containing dormant BHs, which may not have been detected before. The study of this population will provide new information on the BH-mass distribution in binaries and shed light on their formation mechanisms and progenitors. As part of the validation efforts in preparation for the fourth Gaia data release (DR4), we analysed the preliminary astrometric binary solutions, obtained by the Gaia Non-Single Star pipeline, to verify their significance and to minimise false-detection rates in high-mass-function orbital solutions. The astrometric binary solution of one source, Gaia BH3, implies the presence of a 32.70 \pm 0.82 M\odot BH in a binary system with a period of 11.6 yr. Gaia radial velocities independently validate the astrometric orbit. Broad-band photometric and spectroscopic data show that the visible component is an old, very metal-poor giant of the Galactic halo, at a distance of 590 pc. The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known thus far. The low metallicity of the star companion supports the scenario that metal-poor massive stars are progenitors of the high-mass BHs detected by gravitational-wave telescopes. The Galactic orbit of the system and its metallicity indicate that it might belong to the Sequoia halo substructure. Alternatively, and more plausibly, it could belong to the ED-2 stream, which likely originated from a globular cluster that had been disrupted by the Milky Way., Comment: 23 pages, accepted fro publication in A&A Letters. New version with small fixes

Published
2024
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3. The rapid onset of stellar bars in the baryon-dominated centers of disk galaxies

Author

Bland-Hawthorn, J., Tepper-Garcia, T., Agertz, O., and Freeman, K.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

Recent observations of high-redshift galactic disks ($z\approx 1-3$) show a strong negative trend in the dark matter fraction $f_{DM}$ with increasing baryonic surface density. For this to be true, the inner baryons must dominate over dark matter in early massive galaxies, as observed in the Milky Way today. If disks are dominant at early times, we show that stellar bars form promptly within these disks, leading to a high bar fraction at early times. New JWST observations provide the best evidence to date for mature stellar bars in this redshift range. The disk mass fraction $f_{disk}$ within $R_s=2.2 R_{disk}$ is the dominant factor in determining how rapidly a bar forms. Using 3D hydro simulations of halo-disk-bulge galaxies, we confirm the "Fujii relation" for the exponential dependence of the bar formation time $\tau_{bar}$ as a function of $f_{disk}$. For $f_{disk} > 0.3$, the bar formation time declines exponentially fast with increasing $f_{disk}$. This relation is a challenge to simulators - barred models with inadequate resolution fall off this curve. Instead of Fujii's arbitrary threshold for when a bar forms, for the first time, we exploit the exponential growth timescale associated with a positive feedback cycle as the bar emerges from the underlying disk. A modified, mass-dependent trend is observed for halos relevant to systems at cosmic noon ($10.5 < \log M_{halo} < 12$), where the bar onset is slower for higher mass halos at a fixed $f_{disk}$. If baryons dominate over dark matter within $R \approx R_s$, we predict that a high fraction of bars will be found in high-redshift disks long before $z = 1$. Due to its widespread use in simulations, we investigate the Efstathiou-Lake-Negroponte criterion for bar instability: this sub-optimal parameter is inversely related to $f_{disk}$, with a secondary dependence on $M_{halo}$., Comment: 27 pages, 8 figures, 1 table - Astrophysical Journal, accepted (9 March 2023)

Published
2023
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4. A barred Milky Way surrogate from an N-body simulation

Author

Tepper-Garcia, T., Bland-Hawthorn, J., Vasiliev, E., Athanassoula, E., Gerhard, O., Quillen, A., McMillan, P., Freeman, K., Lewis, G. F., Teyssier, R., Sharma, S., Hayden, M. R., and Buder, S.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We present an N-body model for the barred Milky Way (MW) galaxy that reproduces many of its properties, including the overall mass distribution, the disc kinematics, and the properties of the central bar. Our high-resolution (N ~ 10^8 particles) simulation, performed with the Ramses code, starts from an axisymmetric non-equilibrium configuration constructed within the AGAMA framework. This is a self-consistent dynamical model of the MW defined by the best available parameters for the dark matter halo, the stellar disc and the bulge. For the known (stellar and gas) disc mass (4.5 x 10^10 Msun) and disc mass fraction at R ~ 2.2 R_d (f_d ~ 0.3 - 0.6), the low mass limit does not yield a bar in a Hubble time. The high mass limit adopted here produces a box/peanut bar within about 2 Gyr with the correct mass (~10^10 Msun), size (~5 kpc) and peak pattern speed (~ 40-45 km/s/kpc). In agreement with earlier work, the bar formation timescale scales inversely with f_d (i.e. log [T/Gyr] ~ 0.60/f_d - 0.83 for 1 < f_d < 0.3). The disc radial heating is strong, but, in contrast to earlier claims, we find that disc vertical heating outside of the box/peanut bulge structure is negligible. The synthetic barred MW exhibits long-term stability, except for the slow decline (roughly -2 km/s/kpc/Gyr) of the bar pattern speed, consistent with recent estimates. If our model is indicative of the Milky Way, we estimate that the bar first emerged 3-4 Gyr ago., Comment: We welcome comments and missing references

Published
2021

5. GASKAP-HI Pilot Survey Science I: ASKAP Zoom Observations of HI Emission in the Small Magellanic Cloud

Author

Pingel, N. M., Dempsey, J., McClure-Griffiths, N. M., Dickey, J. M., Jameson, K. E., Arce, H., Anglada, G., Bland-Hawthorn, J., Breen, S. L., Buckland-Willis, F., Clark, S. E., Dawson, J. R., Dénes, H., Di Teodoro, E. M., For, B. -Q., Foster, Tyler J., Gómez, J. F., Imai, H., Joncas, G., Kim, C. -G., Lee, M. -Y., Lynn, C., Leahy, D., Ma, Y. K., Marchal, A., McConnell, D., Miville-Deschênes, M. -A., Moss, V. A., Murray, C. E., Nidever, D., Peek, J., Stanimirović, S., Staveley-Smith, L., Tepper-Garcia, T., Tremblay, C. D., Uscanga, L., van Loon, J. Th., Vázquez-Semadeni, E., Allison, J. R., Anderson, C. S., Ball, Lewis, Bell, M., Bock, D. C. -J., Bunton, J., Cooray, F. R., Cornwell, T., Koribalski, B. S., Gupta, N., Hayman, D. B., Harvey-Smith, L., Lee-Waddell, K., Ng, A., Phillips, C. J., Voronkov, M., Westmeier, T., and Whiting, M. T.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We present the most sensitive and detailed view of the neutral hydrogen (HI) emission associated with the Small Magellanic Cloud (SMC), through the combination of data from the Australian Square Kilometre Array Pathfinder (ASKAP) and Parkes (Murriyang), as part of the Galactic Australian Square Kilometre Array Pathfinder (GASKAP) pilot survey. These GASKAP-HI pilot observations, for the first time, reveal HI in the SMC on similar physical scales as other important tracers of the interstellar medium, such as molecular gas and dust. The resultant image cube possesses an rms noise level of 1.1 K (1.6 mJy/beam) per 0.98 km s$^{-1}$ spectral channel with an angular resolution of 30$''$ ($\sim$10 pc). We discuss the calibration scheme and the custom imaging pipeline that utilizes a joint deconvolution approach, efficiently distributed across a computing cluster, to accurately recover the emission extending across the entire $\sim$25 deg$^2$ field-of-view. We provide an overview of the data products and characterize several aspects including the noise properties as a function of angular resolution and the represented spatial scales by deriving the global transfer function over the full spectral range. A preliminary spatial power spectrum analysis on individual spectral channels reveals that the power-law nature of the density distribution extends down to scales of 10 pc. We highlight the scientific potential of these data by comparing the properties of an outflowing high velocity cloud with previous ASKAP+Parkes HI test observations., Comment: Accepted for publication in PASA, 34 pages, 18 figures, 5 tables

Published
2021
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6. Revealing the Ionization Properties of the Magellanic Stream using Optical Emission

Author

Barger, K. A., Madsen, G. J., Fox, A. J., Wakker, B. P., Bland-Hawthorn, J., Nidever, D., Haffner, L. M., Antwi-Danso, J., Hernandez, M., Lehner, N., Hill, A. S., Curzons, A., and Tepper-Garcia, T.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

The Magellanic Stream, a gaseous tail that trails behind the Magellanic Clouds, could replenish the Milky Way with a tremendous amount of gas if it reaches the Galactic disk before it evaporates into the halo. To determine how the Magellanic Stream's properties change along its length, we have conducted an observational study of the H-alpha emission, along with other optical warm ionized gas tracers, toward 39 sight lines. Using the Wisconsin H-alpha Mapper telescope, we detect H-alpha emission brighter than 30 - 50 mR in 26 of our 39 sight lines. This H-alpha emission extends more than 2-degree away from the HI emission. By comparing H-alpha and [OI] intensities, we find that regions with log NHI = 19.5 - 20.0 are 16 - 67% ionized. Most of the H-alpha intensities along the Magellanic Stream are much higher than expected if the primary ionization source is photoionization from Magellanic Clouds, the Milky Way, and the extragalactic background. We find that the additional contribution from self ionization through a "shock cascade" that results as the Stream plows through the halo might be sufficient to reproduce the underlying level of H-alpha emission along the Stream. In the sparsely sampled region below the South Galactic Pole, there exists a subset of sight lines with uncharacteristically bright emission, which suggest that gas is being ionized further by an additional source that could be a linked to energetic processes associated with the Galactic center., Comment: Accepted for publication in the Astrophysical Journal on Nov 8, 2017

Published
2017
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7. An HST/COS legacy survey of intervening SiIII absorption in the extended gaseous halos of low-redshift galaxies

Author

Richter, P., Wakker, B. P., Fechner, C., Herenz, P., Tepper-Garcia, T., and Fox, A. J.

Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

Doubly ionized silicon (SiIII) is a powerful tracer of diffuse ionized gas inside and outside of galaxies. It can be observed in the local Universe in ultraviolet (UV) absorption against bright extragalactic background sources. We here present an extensive study of intervening SiIII-selected absorbers and their relation to the circumgalactic medium (CGM) of galaxies at low redshift (z<=0.1), based on the analysis of UV absorption spectra along 303 extragalactic lines of sight obtained with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST). Along a total redshift path of Dz=24 we identify 69 intervening SiIII systems that all show associated absorption from other low and high ions. We derive a bias-corrected number density of dN/dz(SiIII)=2.5 for absorbers with column densities log N(SiIII)>12.2. We develop a geometrical model for the absorption-cross section of the CGM around the local galaxy population and find excellent agreement between the model predictions and the observations. We further compare redshifts and positions of the absorbers with that of ~64,000 galaxies using archival galaxy-survey data. For the majority of the absorbers we identify possible host galaxies within 300 km/s of the absorbers and derive impact parameters rho<200 kpc, demonstrating that the spatial distributions of SiIII absorbers and galaxies are highly correlated. Our study indicates that the majority of SiIII-selected absorbers in our sample trace the CGM of nearby galaxies within their virial radii at a typical covering fraction of ~70 per cent. From a detailed ionization model we estimate that diffuse gas in the CGM around galaxies, as traced by SiIII, contains substantially more baryonic mass than their neutral interstellar medium., Comment: 32 pages, 17 figures; final version accepted for publication in A&A

Published
2015
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8. Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry

Author

Panuzzo, P., Mazeh, T., Arenou, F., Holl, B., Caffau, E., Jorissen, A., Babusiaux, C., Gavras, P., Sahlmann, J., Bastian, U., Wyrzykowski, Ł., Eyer, L., Leclerc, N., Bauchet, N., Bombrun, A., Mowlavi, N., Seabroke, G. M., Teyssier, D., Balbinot, E., Helmi, A., Brown, A. G.A., Vallenari, A., Prusti, T., De Bruijne, J. H.J., Barbier, A., Biermann, M., Creevey, O. L., Ducourant, C., Evans, D. W., Guerra, R., Hutton, A., Jordi, C., Klioner, S. A., Lammers, U., Lindegren, L., Luri, X., Mignard, F., Nicolas, C., Randich, S., Sartoretti, P., Smiljanic, R., Tanga, P., Walton, N. A., Aerts, C., Bailer-Jones, C. A.L., Cropper, M., Drimmel, R., Jansen, F., Katz, D., Lattanzi, M. G., Soubiran, C., Thévenin, F., Van Leeuwen, F., Andrae, R., Audard, M., Bakker, J., Blomme, R., Castañeda, J., De Angeli, F., Fabricius, C., Fouesneau, M., Frémat, Y., Galluccio, L., Guerrier, A., Heiter, U., Masana, E., Messineo, R., Nienartowicz, K., Pailler, F., Riclet, F., Roux, W., Sordo, R., Gracia-Abril, G., Portell, J., Altmann, M., Benson, K., Berthier, J., Burgess, P. W., Busonero, D., Busso, G., Cacciari, C., Cánovas, H., Carrasco, J. M., Carry, B., Cellino, A., Cheek, N., Clementini, G., Damerdji, Y., Davidson, M., De Teodoro, P., Delchambre, L., Della Oro, A., Fraile Garcia, E., Garabato, D., García-Lario, P., Haigron, R., Hambly, N. C., Harrison, D. L., Hatzidimitriou, D., Hernández, J., Hestroffer, D., Hodgkin, S. T., Jamal, S., Jevardat De Fombelle, G., Jordan, S., Krone-Martins, A., Lanzafame, A. C., Löffler, W., Lorca, A., Marchal, O., Marrese, P. M., Moitinho, A., Muinonen, K., Nuñez Campos, M., Oreshina-Slezak, I., Osborne, P., Pancino, E., Pauwels, T., Recio-Blanco, A., Riello, M., Rimoldini, L., Robin, A. C., Roegiers, T., Sarro, L. M., Schultheis, M., Smith, M., Sozzetti, A., Utrilla, E., Van Leeuwen, M., Weingrill, K., Abbas, U., Ábrahám, P., Abreu Aramburu, A., Ahmed, S., Altavilla, G., Álvarez, M. A., Anders, F., Anderson, R. I., Anglada Varela, E., Antoja, T., Baig, S., Baines, D., Baker, S. G., Balaguer-Núñez, L., Balog, Z., Barache, C., Barros, M., Barstow, M. A., Bartolomé, S., Bashi, D., Bassilana, J. L., Baudeau, N., Becciani, U., Bedin, L. R., Bellas-Velidis, I., Bellazzini, M., Beordo, W., Bernet, M., Bertolotto, C., Bertone, S., Bianchi, L., Binnenfeld, A., Blanco-Cuaresma, S., Bland-Hawthorn, J., Blazere, A., Boch, T., Bossini, D., Bouquillon, S., Bragaglia, A., Braine, J., Bratsolis, E., Breedt, E., Bressan, A., Brouillet, N., Brugaletta, E., Bucciarelli, B., Butkevich, A. G., Buzzi, R., Camut, A., Cancelliere, R., Cantat-Gaudin, T., Capilla Guilarte, D., Carballo, R., Carlucci, T., Carnerero, M. I., Carretero, J., Carton, S., Casamiquela, L., Casey, A., Castellani, M., Castro-Ginard, A., Ceraj, L., Cesare, V., Charlot, P., Chaudet, C., Chemin, L., Chiavassa, A., Chornay, N., Chosson, D., Cooper, W. J., Cornez, T., Cowell, S., Crosta, M., Crowley, C., Cruz Reyes, M., Dafonte, C., Dal Ponte, M., David, M., De Laverny, P., De Luise, F., De March, R., De Torres, A., Del Peloso, E. F., Delbo, M., Delgado, A., Delisle, J. B., Demouchy, C., Denis, E., Dharmawardena, T. E., Di Giacomo, F., Diener, C., Distefano, E., Dolding, C., Dsilva, K., Enke, H., Fabre, C., Fabrizio, M., Faigler, S., Fatoviä, M., Fedorets, G., Fernández-Hernández, J., Fernique, P., Figueras, F., Fouron, C., Fragkoudi, F., Gai, M., Galinier, M., Garcia-Serrano, A., García-Torres, M., Garofalo, A., Gerlach, E., Geyer, R., Giacobbe, P., Gilmore, G., Girona, S., Giuffrida, G., Gomboc, A., Gomez, A., González-Santamaría, I., Gosset, E., Granvik, Mikael, Gregori Barrera, V., Gutiérrez-Sánchez, R., Haywood, M., Helmer, A., Hidalgo, S. L., Hilger, T., Hobbs, D., Hottier, C., Huckle, H. E., Jiménez-Arranz, Ó., Juaristi Campillo, J., Kaczmarek, Z., Kervella, P., Khanna, S., Kontizas, M., Kordopatis, G., Korn, A. J., Kóspál, Á., Kostrzewa-Rutkowska, Z., Kruszyåà  Ska, K., Kun, M., Lambert, S., Lanza, A. F., Lebreton, Y., Lebzelter, T., Leccia, S., Lecoutre, G., Liao, S., Liberato, L., Licata, E., Livanou, E., Lobel, A., López-Miralles, J., Loup, C., Madarász, M., Mahy, L., Mann, R. G., Manteiga, M., Marcellino, C. P., Marchant, J. M., Marconi, M., Marín Pina, D., Marinoni, S., Marshall, D. J., Martín Lozano, J., Martin Polo, L., Martín-Fleitas, J. M., Marton, G., Mascarenhas, D., Masip, A., Mastrobuono-Battisti, A., McMillan, P. J., Meichsner, J., Merc, J., Messina, S., Millar, N. R., Mints, A., Mohamed, D., Molina, D., Molinaro, R., Molnár, L., Monguió, M., Montegriffo, P., Monti, L., Mora, A., Morbidelli, R., Morris, D., Mudimadugula, R., Muraveva, T., Musella, I., Nagy, Z., Nardetto, N., Navarrete, C., Oh, S., Ordenovic, C., Orenstein, O., Pagani, C., Pagano, I., Palaversa, L., Palicio, P. A., Pallas-Quintela, L., Pawlak, M., Penttilä, A., Pesciullesi, P., Pinamonti, M., Plachy, E., Planquart, L., Plum, G., Poggio, E., Pourbaix, D., Price-Whelan, A. M., Pulone, L., Rabin, V., Rainer, M., Raiteri, C. M., Ramos, P., Ramos-Lerate, M., Ratajczak, M., Re Fiorentin, P., Regibo, S., Reylé, C., Ripepi, V., Riva, A., Rix, H. W., Rixon, G., Robert, G., Robichon, N., Robin, C., Romero-Gómez, M., Rowell, N., Ruz Mieres, D., Rybicki, K. A., Sadowski, G., Sagristà Sellés, A., Sanna, N., Santoveña, R., Sarasso, M., Sarmiento, M. H., Sarrate Riera, C., Sciacca, E., Ségransan, D., Semczuk, M., Shahaf, S., Siebert, A., Slezak, E., Smart, R. L., Snaith, O. N., Solano, E., Solitro, F., Souami, D., Souchay, J., Spitoni, E., Spoto, F., Squillante, L. A., Steele, I. A., Steidelmüller, H., Surdej, J., Szabados, L., Taris, F., Taylor, M. B., Teixeira, R., Tepper-Garcia, T., Thuillot, W., Tolomei, L., Tonello, N., Torra, F., Torralba Elipe, G., Trabucchi, M., Trentin, E., Tsantaki, M., Turon, C., Ulla, A., Unger, N., Valtchanov, I., Vanel, O., Vecchiato, A., Vicente, D., Villar, E., Weiler, M., Zhao, H., Zorec, J., Zucker, S., Župiä, A., Zwitter, T., Panuzzo, P., Mazeh, T., Arenou, F., Holl, B., Caffau, E., Jorissen, A., Babusiaux, C., Gavras, P., Sahlmann, J., Bastian, U., Wyrzykowski, Ł., Eyer, L., Leclerc, N., Bauchet, N., Bombrun, A., Mowlavi, N., Seabroke, G. M., Teyssier, D., Balbinot, E., Helmi, A., Brown, A. G.A., Vallenari, A., Prusti, T., De Bruijne, J. H.J., Barbier, A., Biermann, M., Creevey, O. L., Ducourant, C., Evans, D. W., Guerra, R., Hutton, A., Jordi, C., Klioner, S. A., Lammers, U., Lindegren, L., Luri, X., Mignard, F., Nicolas, C., Randich, S., Sartoretti, P., Smiljanic, R., Tanga, P., Walton, N. A., Aerts, C., Bailer-Jones, C. A.L., Cropper, M., Drimmel, R., Jansen, F., Katz, D., Lattanzi, M. G., Soubiran, C., Thévenin, F., Van Leeuwen, F., Andrae, R., Audard, M., Bakker, J., Blomme, R., Castañeda, J., De Angeli, F., Fabricius, C., Fouesneau, M., Frémat, Y., Galluccio, L., Guerrier, A., Heiter, U., Masana, E., Messineo, R., Nienartowicz, K., Pailler, F., Riclet, F., Roux, W., Sordo, R., Gracia-Abril, G., Portell, J., Altmann, M., Benson, K., Berthier, J., Burgess, P. W., Busonero, D., Busso, G., Cacciari, C., Cánovas, H., Carrasco, J. M., Carry, B., Cellino, A., Cheek, N., Clementini, G., Damerdji, Y., Davidson, M., De Teodoro, P., Delchambre, L., Della Oro, A., Fraile Garcia, E., Garabato, D., García-Lario, P., Haigron, R., Hambly, N. C., Harrison, D. L., Hatzidimitriou, D., Hernández, J., Hestroffer, D., Hodgkin, S. T., Jamal, S., Jevardat De Fombelle, G., Jordan, S., Krone-Martins, A., Lanzafame, A. C., Löffler, W., Lorca, A., Marchal, O., Marrese, P. M., Moitinho, A., Muinonen, K., Nuñez Campos, M., Oreshina-Slezak, I., Osborne, P., Pancino, E., Pauwels, T., Recio-Blanco, A., Riello, M., Rimoldini, L., Robin, A. C., Roegiers, T., Sarro, L. M., Schultheis, M., Smith, M., Sozzetti, A., Utrilla, E., Van Leeuwen, M., Weingrill, K., Abbas, U., Ábrahám, P., Abreu Aramburu, A., Ahmed, S., Altavilla, G., Álvarez, M. A., Anders, F., Anderson, R. I., Anglada Varela, E., Antoja, T., Baig, S., Baines, D., Baker, S. G., Balaguer-Núñez, L., Balog, Z., Barache, C., Barros, M., Barstow, M. A., Bartolomé, S., Bashi, D., Bassilana, J. L., Baudeau, N., Becciani, U., Bedin, L. R., Bellas-Velidis, I., Bellazzini, M., Beordo, W., Bernet, M., Bertolotto, C., Bertone, S., Bianchi, L., Binnenfeld, A., Blanco-Cuaresma, S., Bland-Hawthorn, J., Blazere, A., Boch, T., Bossini, D., Bouquillon, S., Bragaglia, A., Braine, J., Bratsolis, E., Breedt, E., Bressan, A., Brouillet, N., Brugaletta, E., Bucciarelli, B., Butkevich, A. G., Buzzi, R., Camut, A., Cancelliere, R., Cantat-Gaudin, T., Capilla Guilarte, D., Carballo, R., Carlucci, T., Carnerero, M. I., Carretero, J., Carton, S., Casamiquela, L., Casey, A., Castellani, M., Castro-Ginard, A., Ceraj, L., Cesare, V., Charlot, P., Chaudet, C., Chemin, L., Chiavassa, A., Chornay, N., Chosson, D., Cooper, W. J., Cornez, T., Cowell, S., Crosta, M., Crowley, C., Cruz Reyes, M., Dafonte, C., Dal Ponte, M., David, M., De Laverny, P., De Luise, F., De March, R., De Torres, A., Del Peloso, E. F., Delbo, M., Delgado, A., Delisle, J. B., Demouchy, C., Denis, E., Dharmawardena, T. E., Di Giacomo, F., Diener, C., Distefano, E., Dolding, C., Dsilva, K., Enke, H., Fabre, C., Fabrizio, M., Faigler, S., Fatoviä, M., Fedorets, G., Fernández-Hernández, J., Fernique, P., Figueras, F., Fouron, C., Fragkoudi, F., Gai, M., Galinier, M., Garcia-Serrano, A., García-Torres, M., Garofalo, A., Gerlach, E., Geyer, R., Giacobbe, P., Gilmore, G., Girona, S., Giuffrida, G., Gomboc, A., Gomez, A., González-Santamaría, I., Gosset, E., Granvik, Mikael, Gregori Barrera, V., Gutiérrez-Sánchez, R., Haywood, M., Helmer, A., Hidalgo, S. L., Hilger, T., Hobbs, D., Hottier, C., Huckle, H. E., Jiménez-Arranz, Ó., Juaristi Campillo, J., Kaczmarek, Z., Kervella, P., Khanna, S., Kontizas, M., Kordopatis, G., Korn, A. J., Kóspál, Á., Kostrzewa-Rutkowska, Z., Kruszyåà  Ska, K., Kun, M., Lambert, S., Lanza, A. F., Lebreton, Y., Lebzelter, T., Leccia, S., Lecoutre, G., Liao, S., Liberato, L., Licata, E., Livanou, E., Lobel, A., López-Miralles, J., Loup, C., Madarász, M., Mahy, L., Mann, R. G., Manteiga, M., Marcellino, C. P., Marchant, J. M., Marconi, M., Marín Pina, D., Marinoni, S., Marshall, D. J., Martín Lozano, J., Martin Polo, L., Martín-Fleitas, J. M., Marton, G., Mascarenhas, D., Masip, A., Mastrobuono-Battisti, A., McMillan, P. J., Meichsner, J., Merc, J., Messina, S., Millar, N. R., Mints, A., Mohamed, D., Molina, D., Molinaro, R., Molnár, L., Monguió, M., Montegriffo, P., Monti, L., Mora, A., Morbidelli, R., Morris, D., Mudimadugula, R., Muraveva, T., Musella, I., Nagy, Z., Nardetto, N., Navarrete, C., Oh, S., Ordenovic, C., Orenstein, O., Pagani, C., Pagano, I., Palaversa, L., Palicio, P. A., Pallas-Quintela, L., Pawlak, M., Penttilä, A., Pesciullesi, P., Pinamonti, M., Plachy, E., Planquart, L., Plum, G., Poggio, E., Pourbaix, D., Price-Whelan, A. M., Pulone, L., Rabin, V., Rainer, M., Raiteri, C. M., Ramos, P., Ramos-Lerate, M., Ratajczak, M., Re Fiorentin, P., Regibo, S., Reylé, C., Ripepi, V., Riva, A., Rix, H. W., Rixon, G., Robert, G., Robichon, N., Robin, C., Romero-Gómez, M., Rowell, N., Ruz Mieres, D., Rybicki, K. A., Sadowski, G., Sagristà Sellés, A., Sanna, N., Santoveña, R., Sarasso, M., Sarmiento, M. H., Sarrate Riera, C., Sciacca, E., Ségransan, D., Semczuk, M., Shahaf, S., Siebert, A., Slezak, E., Smart, R. L., Snaith, O. N., Solano, E., Solitro, F., Souami, D., Souchay, J., Spitoni, E., Spoto, F., Squillante, L. A., Steele, I. A., Steidelmüller, H., Surdej, J., Szabados, L., Taris, F., Taylor, M. B., Teixeira, R., Tepper-Garcia, T., Thuillot, W., Tolomei, L., Tonello, N., Torra, F., Torralba Elipe, G., Trabucchi, M., Trentin, E., Tsantaki, M., Turon, C., Ulla, A., Unger, N., Valtchanov, I., Vanel, O., Vecchiato, A., Vicente, D., Villar, E., Weiler, M., Zhao, H., Zorec, J., Zucker, S., Župiä, A., and Zwitter, T.

Abstract

Context. Gravitational waves from black-hole (BH) merging events have revealed a population of extra-galactic BHs residing in short-period binaries with masses that are higher than expected based on most stellar evolution models-And also higher than known stellar-origin black holes in our Galaxy. It has been proposed that those high-mass BHs are the remnants of massive metal-poor stars. Aims. Gaia astrometry is expected to uncover many Galactic wide-binary systems containing dormant BHs, which may not have been detected before. The study of this population will provide new information on the BH-mass distribution in binaries and shed light on their formation mechanisms and progenitors. Methods. As part of the validation efforts in preparation for the fourth Gaia data release (DR4), we analysed the preliminary astrometric binary solutions, obtained by the Gaia Non-Single Star pipeline, to verify their significance and to minimise false-detection rates in high-mass-function orbital solutions. Results. The astrometric binary solution of one source, Gaia BH3, implies the presence of a 32.70a ±a 0.82aM- BH in a binary system with a period of 11.6 yr. Gaia radial velocities independently validate the astrometric orbit. Broad-band photometric and spectroscopic data show that the visible component is an old, very metal-poor giant of the Galactic halo, at a distance of 590 pc. Conclusions. The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known thus far. The low metallicity of the star companion supports the scenario that metal-poor massive stars are progenitors of the high-mass BHs detected by gravitational-wave telescopes. The Galactic orbit of the system and its metallicity indicate that it might belong to the Sequoia halo substructure. Alternatively, and more plausibly, it could belong to the ED-2 stream, which likely originated from a globular cluster that had been disrupted by the Milky Way., Funder: for funder information see Appendix F in https://doi.org/10.1051/0004-6361/202449763;Full text license: CC BY 4.0

Published
2024
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9. GASKAP-HI pilot survey science I: ASKAP zoom observations of Hi emission in the Small Magellanic Cloud

Author

Pingel, NM, Dempsey, J, McClure-Griffiths, NM, Dickey, JM, Jameson, KE, Arce, H, Anglada, G, Bland-Hawthorn, J, Breen, SL, Buckland-Willis, F, Clark, SE, Dawson, JR, Dénes, H, Di Teodoro, EM, For, BQ, Foster, TJ, Gómez, JF, Imai, H, Joncas, G, Kim, CG, Lee, MY, Lynn, C, Leahy, D, Ma, YK, Marchal, A, McConnell, D, Miville-Deschènes, MA, Moss, VA, Murray, CE, Nidever, D, Peek, J, Stanimirović, S, Staveley-Smith, L, Tepper-Garcia, T, Tremblay, CD, Uscanga, L, Van Loon, JT, Vázquez-Semadeni, E, Allison, JR, Anderson, CS, Ball, L, Bell, M, Bock, DCJ, Bunton, J, Cooray, FR, Cornwell, T, Koribalski, BS, Gupta, N, Hayman, DB, Harvey-Smith, L, Lee-Waddell, K, Ng, A, Phillips, CJ, Voronkov, M, Westmeier, T, Whiting, MT, Pingel, NM, Dempsey, J, McClure-Griffiths, NM, Dickey, JM, Jameson, KE, Arce, H, Anglada, G, Bland-Hawthorn, J, Breen, SL, Buckland-Willis, F, Clark, SE, Dawson, JR, Dénes, H, Di Teodoro, EM, For, BQ, Foster, TJ, Gómez, JF, Imai, H, Joncas, G, Kim, CG, Lee, MY, Lynn, C, Leahy, D, Ma, YK, Marchal, A, McConnell, D, Miville-Deschènes, MA, Moss, VA, Murray, CE, Nidever, D, Peek, J, Stanimirović, S, Staveley-Smith, L, Tepper-Garcia, T, Tremblay, CD, Uscanga, L, Van Loon, JT, Vázquez-Semadeni, E, Allison, JR, Anderson, CS, Ball, L, Bell, M, Bock, DCJ, Bunton, J, Cooray, FR, Cornwell, T, Koribalski, BS, Gupta, N, Hayman, DB, Harvey-Smith, L, Lee-Waddell, K, Ng, A, Phillips, CJ, Voronkov, M, Westmeier, T, and Whiting, MT

Abstract

We present the most sensitive and detailed view of the neutral hydrogen emission associated with the Small Magellanic Cloud (SMC), through the combination of data from the Australian Square Kilometre Array Pathfinder (ASKAP) and Parkes (Murriyang), as part of the Galactic Australian Square Kilometre Array Pathfinder (GASKAP) pilot survey. These GASKAP-HI pilot observations, for the first time, reveal in the SMC on similar physical scales as other important tracers of the interstellar medium, such as molecular gas and dust. The resultant image cube possesses an rms noise level of 1.1 K spectral channel with an angular resolution of . We discuss the calibration scheme and the custom imaging pipeline that utilises a joint deconvolution approach, efficiently distributed across a computing cluster, to accurately recover the emission extending across the entire field-of-view. We provide an overview of the data products and characterise several aspects including the noise properties as a function of angular resolution and the represented spatial scales by deriving the global transfer function over the full spectral range. A preliminary spatial power spectrum analysis on individual spectral channels reveals that the power law nature of the density distribution extends down to scales of 10 pc. We highlight the scientific potential of these data by comparing the properties of an outflowing high-velocity cloud with previous ASKAP+Parkes test observations.

Published
2022

10. GASKAP-HI pilot survey science I: ASKAP zoom observations of Hi emission in the Small Magellanic Cloud

Author

Pingel, N. M., primary, Dempsey, J., additional, McClure-Griffiths, N. M., additional, Dickey, J. M., additional, Jameson, K. E., additional, Arce, H., additional, Anglada, G., additional, Bland-Hawthorn, J., additional, Breen, S. L., additional, Buckland-Willis, F., additional, Clark, S. E., additional, Dawson, J. R., additional, Dénes, H., additional, Di Teodoro, E. M., additional, For, B.-Q., additional, Foster, Tyler J., additional, Gómez, J. F., additional, Imai, H., additional, Joncas, G., additional, Kim, C.-G., additional, Lee, M.-Y., additional, Lynn, C., additional, Leahy, D., additional, Ma, Y. K., additional, Marchal, A., additional, McConnell, D., additional, Miville-Deschènes, M.-A., additional, Moss, V. A., additional, Murray, C. E., additional, Nidever, D., additional, Peek, J., additional, Stanimirović, S., additional, Staveley-Smith, L., additional, Tepper-Garcia, T., additional, Tremblay, C. D., additional, Uscanga, L., additional, van Loon, J. Th., additional, Vázquez-Semadeni, E., additional, Allison, J. R., additional, Anderson, C. S., additional, Ball, Lewis, additional, Bell, M., additional, Bock, D. C.-J., additional, Bunton, J., additional, Cooray, F. R., additional, Cornwell, T., additional, Koribalski, B. S., additional, Gupta, N., additional, Hayman, D. B., additional, Harvey-Smith, L., additional, Lee-Waddell, K., additional, Ng, A., additional, Phillips, C. J., additional, Voronkov, M., additional, Westmeier, T., additional, and Whiting, M. T., additional

Published
2022
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11. Fundamental relations for the velocity dispersion of stars in the Milky Way

Author

Sharma, S, Hayden, MR, Bland-Hawthorn, J, Stello, D, Buder, S, Zinn, JC, Kallinger, T, Asplund, M, De Silva, GM, D'Orazi, V, Freeman, K, Kos, J, Lewis, GF, Lin, J, Lind, K, Martell, S, Simpson, JD, Wittenmyer, RA, Zucker, DB, Zwitter, T, Chen, B, Cotar, K, Esdaile, J, Hon, M, Horner, J, Huber, D, Kafle, PR, Khanna, S, Ting, YS, Nataf, DM, Nordlander, T, Saadon, MHM, Tepper-Garcia, T, Tinney, CG, Traven, G, Watson, F, Wright, D, Wyse, RFG, Sharma, S, Hayden, MR, Bland-Hawthorn, J, Stello, D, Buder, S, Zinn, JC, Kallinger, T, Asplund, M, De Silva, GM, D'Orazi, V, Freeman, K, Kos, J, Lewis, GF, Lin, J, Lind, K, Martell, S, Simpson, JD, Wittenmyer, RA, Zucker, DB, Zwitter, T, Chen, B, Cotar, K, Esdaile, J, Hon, M, Horner, J, Huber, D, Kafle, PR, Khanna, S, Ting, YS, Nataf, DM, Nordlander, T, Saadon, MHM, Tepper-Garcia, T, Tinney, CG, Traven, G, Watson, F, Wright, D, and Wyse, RFG

Abstract

We explore the fundamental relations governing the radial and vertical velocity dispersions of stars in the Milky Way, from combined studies of complementary surveys including GALAH, LAMOST, APOGEE, the NASA Kepler and K2 missions, and Gaia DR2. We find that different stellar samples, even though they target different tracer populations and employ a variety of age estimation techniques, follow the same set of fundamental relations. We provide the clearest evidence to date that, in addition to the well-known dependence on stellar age, the velocity dispersions of stars depend on orbital angular momentum Lz, metallicity, and height above the plane |z|, and are well described by a multiplicatively separable functional form. The dispersions have a power-law dependence on age with exponents of 0.441 ± 0.007 and 0.251 ± 0.006 for σz and σR, respectively, and the power law is valid even for the oldest stars. For the solar neighbourhood stars, the apparent break in the power law for older stars, as seen in previous studies, is due to the anticorrelation of Lz with age. The dispersions decrease with increasing Lz until we reach the Sun's orbital angular momentum, after which σz increases (implying flaring in the outer disc) while σR flattens. For a given age, the dispersions increase with decreasing metallicity, suggesting that the dispersions increase with birth radius. The dispersions also increase linearly with |z|. The same set of relations that work in the solar neighbourhood also work for stars between 3 < R/kpc < 20. Finally, the high-[α/Fe] stars follow the same relations as the low-[α/Fe] stars.

Published
2021

12. The GALAH survey and Gaia DR2: Dissecting the stellar disc's phase space by age, action, chemistry, and location

Author

Bland-Hawthorn, J, Sharma, S, Tepper-Garcia, T, Binney, J, Freeman, KC, Hayden, MR, Kos, J, De Silva, GM, Ellis, S, Lewis, GF, Asplund, M, Buder, S, Casey, AR, D'Orazi, V, Duong, L, Khanna, S, Lin, J, Lind, K, Martell, SL, Ness, MK, Simpson, JD, Zucker, DB, Zwitter, T, Kafle, PR, Quillen, AC, Ting, YS, Wyse, RFG, Bland-Hawthorn, J, Sharma, S, Tepper-Garcia, T, Binney, J, Freeman, KC, Hayden, MR, Kos, J, De Silva, GM, Ellis, S, Lewis, GF, Asplund, M, Buder, S, Casey, AR, D'Orazi, V, Duong, L, Khanna, S, Lin, J, Lind, K, Martell, SL, Ness, MK, Simpson, JD, Zucker, DB, Zwitter, T, Kafle, PR, Quillen, AC, Ting, YS, and Wyse, RFG

Abstract

We use the second data releases of the European Space AgencyGaia astrometric survey and the high-resolution Galactic Archaeology with HERMES (GALAH) spectroscopic survey to analyse the structure of our Galaxy's disc components. With GALAH, we separate the α-rich and α-poor discs (with respect to Fe), which are superposed in both position and velocity space, and examine their distributions in action space. We study the distribution of stars in the zVz phase plane, for both Vφ and VR, and recover the remarkable 'phase spiral' discovered by Gaia. We identify the anticipated quadrupole signature in zVz of a tilted velocity ellipsoid for stars above and below the Galactic plane. By connecting our work with earlier studies, we show that the phase spiral is likely to extend well beyond the narrow solar neighbourhood cylinder in which it was found. The phase spiral is a signature of corrugated waves that propagate through the disc, and the associated non-equilibrium phase mixing. The radially asymmetric distribution of stars involved in the phase spiral reveals that the corrugation, which is mostly confined to the α-poor disc, grows in z-amplitude with increasing radius. We present new simulations of tidal disturbance of the Galactic disc by the Sagittarius (Sgr) dwarf. The effect on the zVz phase plane lasts ≥2Gyr, but a subsequent disc crossing wipes out the coherent structure. We find that the phase spiral was excited ≤0.5 Gyr ago by an object like Sgr with total mass ∼3 × 1010 M⊙ (stripped down from ∼5 × 1010 M⊙ when it first entered the halo) passing through the plane.

Published
2019

13. The GALAH survey and Gaia DR2: Linking ridges, arches, and vertical waves in the kinematics of the Milky Way

Author

Khanna, S, Sharma, S, Tepper-Garcia, T, Bland-Hawthorn, J, Hayden, M, Asplund, M, Buder, S, Chen, B, De Silva, GM, Freeman, KC, Kos, J, Lewis, GF, Lin, J, Martell, SL, Simpson, JD, Nordlander, T, Stello, D, Ting, YS, Zucker, DB, Zwitter, T, Khanna, S, Sharma, S, Tepper-Garcia, T, Bland-Hawthorn, J, Hayden, M, Asplund, M, Buder, S, Chen, B, De Silva, GM, Freeman, KC, Kos, J, Lewis, GF, Lin, J, Martell, SL, Simpson, JD, Nordlander, T, Stello, D, Ting, YS, Zucker, DB, and Zwitter, T

Abstract

Gaia DR2 has revealed new small-scale and large-scale patterns in the phase-space distribution of stars in the Milky Way. In cylindrical Galactic coordinates (R, φ, z), ridge-like structures can be seen in the (R, Vφ) plane and asymmetric arch-like structures in the (VR, Vφ) plane. We show that the ridges are also clearly present when the third dimension of the (R, Vφ) plane is represented by z, Vz, VR, [Fe/H], and [α/Fe]. The maps suggest that stars along the ridges lie preferentially close to the Galactic mid-plane (|z| < 0.2 kpc), and have metallicity and α elemental abundance similar to that of the Sun. We show that phase mixing of disrupting spiral arms can generate both the ridges and the arches. It also generates discrete groupings in orbital energy − the ridges and arches are simply surfaces of constant energy. We identify eight distinct ridges in the Gaia DR2 data: six of them have constant energy while two have constant angular momentum. Given that the signature is strongest for stars close to the plane, the presence of ridges in z and Vz suggests a coupling between planar and vertical directions. We demonstrate, using N-body simulations that such coupling can be generated both in isolated discs and in discs perturbed by an orbiting satellite like the Sagittarius dwarf galaxy.

Published
2019

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