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Horta, D and Schiavon, RP (2025) Modelling the density and mass of the Milky Way's proto-galaxy components with APOGEE-Gaia. Monthly Notices of the Royal Astronomical Society, 537 (4). pp. 3730-3745. ISSN 0035-8711
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Modelling the density and mass of the Milky Way's proto-galaxy components with $APOGEE$-$Gaia$.pdf - Published Version Available under License Creative Commons Attribution. Download (4MB) | Preview |
Abstract
Unravelling galaxy formation theory requires understanding galaxies both at high and low redshifts. A possible way to connect both realms is by studying the oldest stars in the Milky Way (i.e., the proto-Galaxy). We use the APOGEE-Gaia surveys to perform a purely chemical dissection of Milky Way (MW) stellar populations, and identify samples of stars likely belonging to proto-Galactic fragments. The metallicity dependence of the distribution of old MW stars in the [Mg/Mn]-[Al/Fe] enables the distinction of at least two populations in terms of their star formation histories: a rapidly evolved population likely associated with the main progenitor system of the proto-MW; and populations characterised by less efficient, slower, star formation. In the Solar neighbourhood less efficient star forming populations are dominated by the Gaia-Enceladus/Sausage accretion debris. In the inner Galaxy, they are largely associated with the $Heracles$ structure. We model the density of
chemically defined proto-Galaxy populations, finding that they are well represented by a Plummer model with a scale radius of a\sim3.5 kpc, and an oblate ellipsoid with flattening parameters [p\sim0.8; q\sim0.6]; this finding indicates that the MW plausibly hosts a low-mass, metal-poor, bulge component. We integrate this density for chemically unevolved stars between -2 < \mathrm{[Fe/H]} < -0.5$ to obtain a minimum stellar mass for the proto-Galaxy of M_{*} (r<10~\mathrm{kpc}) = 9.1\pm0.2\times10^{8} M_{\odot}$. Our results suggest the proto-Milky Way is at least comprised of two significant fragments: the main in situ progenitor and the Heracles structure.
| Item Type: | Article |
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| Uncontrolled Keywords: | astro-ph.GA; astro-ph.GA; astro-ph.GA; astro-ph.GA; 5109 Space Sciences; 5101 Astronomical Sciences; 51 Physical Sciences; 5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | Oxford University Press |
| SWORD Depositor: | A Symplectic |
| Date Deposited: | 25 Apr 2025 15:30 |
| Last Modified: | 25 Apr 2025 15:30 |
| DOI or ID number: | 10.1093/mnras/staf256 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/26267 |
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