Towards understanding the Milky Way’s typicality: assessing the chemodynamics of M31’s bulge and bar, thick and thin discs
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No Canadian affiliation. An affiliation-only frame — the usual design — would never have seen this work. It is one of the works that make the case for inverting the frame.
The three-model screen
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Chemodynamic modelling of M31's stellar populations; domain astrophysics.
This astronomy study models stellar populations in Andromeda, not research.
Astrophysics modelling of M31 stellar populations and galactic structure.
Abstract
ABSTRACT We describe a novel framework to model galaxy spectra with two cospatial stellar populations, such as may represent a bulge and bar or thick and thin disc, and apply it to APOGEE spectra in the inner $\sim$2 kpc of M31, as well as to stacked spectra representative of the northern and southern parts of M31’s disc ($R\sim 4\!-\!7$ kpc). We use a new unWISE-based photometric decomposition of M31 that includes a Sérsic bulge, bar, and exponential disc. This informs our full-spectrum fitting with A-LIST spectral templates to derive the radial velocity, velocity dispersion, metallicity, and $\alpha$ abundance for both components in each spectrum. In the bulge, one component exhibits little net rotation, high velocity dispersion ($\sim$170 km s$^{-1}$), an average [M/H] = 0.07, and average [$\alpha$/M] = 0.29, while the second component shows structured rotation, lower velocity dispersion ($\sim$121 km s$^{-1}$), and similar average abundances. We also constrain the abundance gradients for each of these components. We tentatively associate the first component with the classical bulge and the second with the bar. In the north disc we identify two distinct components: the first with hotter kinematics, lower metallicity, and higher $\alpha$ abundance than the second ([M/H] = 0.1 and 0.39, [$\alpha$/M] = 0.29 and 0.07). These discs appear comparable to the Milky Way’s ‘thick’ and ‘thin’ discs, providing the first evidence that M31’s inner disc has a similar chemodynamical structure. Such multipopulation analysis is crucial to constrain galaxy evolution models that strive to recreate the complex stellar populations found in the Milky Way.
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The record
- Venue
- Monthly Notices of the Royal Astronomical Society
- Topic
- Stellar, planetary, and galactic studies
- Field
- Physics and Astronomy
- Canadian institutions
- —
- Funders
- Lawrence Berkeley National LaboratorySmithsonian Astrophysical ObservatoryScience and Technology Facilities CouncilUniversity of Colorado BoulderJet Propulsion LaboratoryInstituto de Astrofísica de CanariasOffice of ScienceMax-Planck-Institut für AstronomieMax-Planck-Institut für AstrophysikUniversity of OxfordYork UniversityUniversidad Nacional Autónoma de MéxicoSpace Telescope Science InstituteLeibniz-GemeinschaftUniversity of Notre DameCarnegie Mellon UniversityOhio State UniversityUniversity of TokyoUniversity of WashingtonAlfred P. Sloan FoundationJohns Hopkins UniversityUniversity of UtahCarnegie Institution of WashingtonSmithsonian InstitutionU.S. Department of EnergyCalifornia Institute of TechnologyMinistério da Ciência, Tecnologia e InovaçãoNational Aeronautics and Space AdministrationNew Mexico State UniversityUniversity of California, Los AngelesUniversity of PortsmouthVanderbilt UniversityYale UniversityNational Science Foundation
- Keywords
- BulgePhysicsAstrophysicsMilky WayVelocity dispersionMetallicitySpectral lineGalaxyGalaxy rotation curveBar (unit)AstronomyGalaxy formation and evolution
- Has abstract in OpenAlex
- yes