Towards Understanding the Milky Way's Typicality: Assessing the Chemodynamics of M31's Bulge & Bar, Thick & Thin Discs
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866912556343361536 |
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| author | Gibson, Benjamin J. Zasowski, Gail Seth, Anil Gadotti, Dimitri A. Wang, Zixian Bizyaev, Dmitry Majewski, Steven R. Holtzmann, Jon Sharma, Sanjib |
| author_facet | Gibson, Benjamin J. Zasowski, Gail Seth, Anil Gadotti, Dimitri A. Wang, Zixian Bizyaev, Dmitry Majewski, Steven R. Holtzmann, Jon Sharma, Sanjib |
| contents | We describe a novel framework to model galaxy spectra with two cospatial stellar populations, such as may represent a bulge & bar or thick & 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\sim4-7$ kpc). We use a custom M31 photometric decomposition and A-LIST spectral templates to derive the radial velocity, velocity dispersion, metallicity, and $α$ abundance for both components in each spectrum. In the bulge, one component exhibits little net rotation, high velocity dispersion ($\sim$170 km s$^{-1}$), near-solar metallicity, and high $α$ abundance ([$α$/M] = 0.28), while the second component shows structured rotation, lower velocity dispersion ($\sim$121 km s$^{-1}$), and slightly higher abundances ([M/H] = 0.09, [$α$/M] = 0.3). 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 $α$ abundance than the second ([M/H] = 0.1 and 0.39, [$α$/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. We do not identify two distinct components in the south, potentially due to effects from recent interactions. Such multi-population analysis is crucial to constrain galaxy evolution models that strive to recreate the complex stellar populations found in the Milky Way. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_23340 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Towards Understanding the Milky Way's Typicality: Assessing the Chemodynamics of M31's Bulge & Bar, Thick & Thin Discs Gibson, Benjamin J. Zasowski, Gail Seth, Anil Gadotti, Dimitri A. Wang, Zixian Bizyaev, Dmitry Majewski, Steven R. Holtzmann, Jon Sharma, Sanjib Astrophysics of Galaxies We describe a novel framework to model galaxy spectra with two cospatial stellar populations, such as may represent a bulge & bar or thick & 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\sim4-7$ kpc). We use a custom M31 photometric decomposition and A-LIST spectral templates to derive the radial velocity, velocity dispersion, metallicity, and $α$ abundance for both components in each spectrum. In the bulge, one component exhibits little net rotation, high velocity dispersion ($\sim$170 km s$^{-1}$), near-solar metallicity, and high $α$ abundance ([$α$/M] = 0.28), while the second component shows structured rotation, lower velocity dispersion ($\sim$121 km s$^{-1}$), and slightly higher abundances ([M/H] = 0.09, [$α$/M] = 0.3). 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 $α$ abundance than the second ([M/H] = 0.1 and 0.39, [$α$/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. We do not identify two distinct components in the south, potentially due to effects from recent interactions. Such multi-population analysis is crucial to constrain galaxy evolution models that strive to recreate the complex stellar populations found in the Milky Way. |
| title | Towards Understanding the Milky Way's Typicality: Assessing the Chemodynamics of M31's Bulge & Bar, Thick & Thin Discs |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2410.23340 |