We analyze the kinematics as a function of stellar age for Andromeda (M31) mass analogs from the IllustrisTNG cosmological simulation. We divide the star particles into four age groups: less than 1 Gyr, 1 to 5 Gyr, 5 to 10 Gyr, and greater 10 Gyr, and compare the kinematics of these groups to that of the neutral gas cells. We calculate rotation curves for the stellar and gaseous components of each analog from 2 kpc to 20 kpc from the center of mass. We find that the lag, or asymmetric drift (AD), between the gas rotation curve and the stellar rotation curve on average increases with stellar age. This finding is consistent with observational measurements of AD in the disk of the Andromeda galaxy. When the M31 analogs are separated into groups based on merger history, we find that there is a difference in the AD of the analogs that have had a 4:1 merger the last 4 Gyr, 8 Gyr, or 12 Gyr compared to analogs that have not experienced a 4:1 merger in the same time frame. The subset of analogs that have had a 4:1 merger within the last 4 Gyr are also similar to AD measurements of stars in the disk of M31, providing evidence that M31 may in fact have recently merged with a galaxy nearly one fourth of its mass. Further work using high resolution zoom in simulations is required to explore the contribution of internal heating to AD.

中文翻译：

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IllustrisTNG 模拟中仙女座类似物的不对称漂移

我们将运动学作为来自 IllustrisTNG 宇宙学模拟的仙女座 (M31) 质量类似物的恒星年龄的函数进行分析。我们将恒星粒子分为四个年龄组：小于 1 Gyr、1 到 5 Gyr、5 到 10 Gyr 和更大的 10 Gyr，并将这些组的运动学与中性气室的运动学进行比较。我们计算了从质量中心 2 kpc 到 20 kpc 的每个类似物的恒星和气体成分的旋转曲线。我们发现气体自转曲线和恒星自转曲线之间的滞后或不对称漂移（AD）平均随着恒星年龄的增加而增加。这一发现与仙女座星系盘中 AD 的观测测量结果一致。当根据合并历史将 M31 类似物分成几组时，我们发现具有 4 的类似物的 AD 存在差异：1 合并最后 4 Gyr、8 Gyr 或 12 Gyr 与未在同一时间范围内经历 4:1 合并的类似物相比。在过去 4 Gyr 内以 4:1 合并的类似物子集也类似于 M31 盘中恒星的 AD 测量值，提供证据表明 M31 实际上最近可能与一个质量接近其四分之一的星系合并. 需要进一步使用高分辨率放大模拟来探索内部加热对 AD 的贡献。