The Chemodynamics of the Stellar Populations in M31 from APOGEE Integrated-light Spectroscopy
The Chemodynamics of the Stellar Populations in M31 from APOGEE Integrated-light Spectroscopy
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用远地点积分光谱学研究M31恒星群的化学动力学
DOI：
10.3847/1538-4357/acd9a9
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
B. J. Gibson;G. Zasowski;A. Seth;Aishwarya Ashok;Kameron Goold;T. Wainer;S. Hasselquist;J. Holtzman;J. Imig;D. Bizyaev;S. Majewski
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文献类型：
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作者：
B. J. Gibson;G. Zasowski;A. Seth;Aishwarya Ashok;Kameron Goold;T. Wainer;S. Hasselquist;J. Holtzman;J. Imig;D. Bizyaev;S. Majewski
我们对M31内部~ 7kpc的远地点近1000个近红外综合光谱进行了分析。我们利用a - list简单恒星人口光谱模板进行全光谱拟合，这些模板代表具有相同年龄，[M/H]和[α/M]的恒星人口。据此，我们确定了M31的棒状、凸起和内盘恒星群的平均运动学、金属丰度、α丰度和年龄（~ 4-7 kpc）。我们在M31中发现了一个非轴对称的速度场，这是由于棒的存在造成的。M31凸起的金属丰度（平均[M/H] = - 0.149 - 0.081+0.067指数）低于圆盘，金属丰度在棒材两侧最小（[M/H] ~ - 0.2）， α丰度增强（平均[α/M] = 0.281 - 0.038+0.035）。在~ 7 kpc范围内，M31盘的金属丰度（[M/H] =−0.023−0.052+0.050）和α丰度（[α/M] = 0.274−0.025+0.020）均有所增强。这两种结构成分均在≃12 Gyr处老化。我们发现平均金属丰度随着距离M31中心的距离而增加，沿圆盘长轴的梯度最大（0.043±0.021指数kpc−1）。这种梯度是由凸出部分和盘状部分的光贡献变化造成的。恒星群的化学动力学编码了关于星系的化学富集、恒星形成历史和合并历史的信息，使我们能够讨论M31形成的新限制。我们的研究结果为我们了解银河系和其他外部星系提供了一块垫脚石。
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, α abundances, 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] = −0.149−0.081+0.067 dex) than the disk, features minima in metallicity on either side of the bar ([M/H] ∼ −0.2), and is enhanced in α abundance (mean [α/M] = 0.281−0.038+0.035 ). The disk of M31 within ∼7 kpc is enhanced in both metallicity ([M/H] = −0.023−0.052+0.050 ) and α abundance ([α/M] = 0.274−0.025+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.