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Title: The Chemodynamics of the Stellar Populations in M31 from APOGEE Integrated-light Spectroscopy

We present an analysis of nearly 1000 near-infrared, integrated-light spectra from APOGEE in the inner ∼7 kpc of M31. We utilize full-spectrum fitting with A-LIST simple stellar population spectral templates that represent a population of stars with the same age, [M/H], and [α/M]. With this, we determine the mean kinematics, metallicities,αabundances, and ages of the stellar populations of M31's bar, bulge, and inner disk (∼4–7 kpc). We find a nonaxisymmetric velocity field in M31 resulting from the presence of a bar. The bulge of M31 is less metal-rich (mean [M/H] =0.1490.081+0.067dex) than the disk, features minima in metallicity on either side of the bar ([M/H] ∼ −0.2), and is enhanced inαabundance (mean [α/M] =0.2810.038+0.035). The disk of M31 within ∼7 kpc is enhanced in both metallicity ([M/H] =0.0230.052+0.050) andαabundance ([α/M] =0.2740.025+0.020). Both of these structural components are uniformly old at ≃12 Gyr. We find the mean metallicity increases with distance from the center of M31, with the steepest gradient along the disk major axis (0.043 ± 0.021 dex kpc−1). This gradient is the result of changing light contributions from the bulge and disk. The chemodynamics of stellar populations encodes information about a galaxy’s chemical enrichment, star formation history, and merger history, allowing us to discuss new constraints on M31's formation. Our results provide a stepping stone between our understanding of the Milky Way and other external galaxies.

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DOI PREFIX: 10.3847
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Journal Name:
The Astrophysical Journal
Medium: X Size: Article No. 23
["Article No. 23"]
Sponsoring Org:
National Science Foundation
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