论文标题

内部和颠倒:气冷却和动态加热在塑造出色的年龄关系中的作用

Inside Out and Upside-Down: The Roles of Gas Cooling and Dynamical Heating in Shaping the Stellar Age-Velocity Relation

论文作者

Bird, Jonathan C., Loebman, Sarah R., Weinberg, David H., Brooks, Alyson, Quinn, Thomas R., Christensen, Charlotte R.

论文摘要

随着时间的推移,使用银河系的单个恒星或全球磁盘运动学的统计研究,可以洞悉磁盘如何形成和进化。我们使用银河系磁盘Galaxy H277的高分辨率,宇宙变焦仿真将局部磁盘运动学和磁盘的演变绑在一起。 H277的当今恒星年龄关系(AVR)几乎与银河系中类似的太阳邻居测量值相同。这一成功的一个关键要素是模拟动态冷的多相ISM,它允许年轻的星星以低速分散体形成($σ_{\ Mathrm {breath}} $$ \ sim 6-8 \ \ \ \ \ \ \ \ \ \ mathrm {km} \ km} \,\,\,\ mathrm {s s s s} s}}^= {-1}年龄较大的恒星天生在运动学上更热(即,随着时间的流逝,磁盘会以“倒置”的地层场景沉降),随后在出生后加热。磁盘还会生长为“内而外”,由于径向混合,存在于$ z = 0 $的太阳能社区中的许多较老的恒星。 We demonstrate that the evolution of $σ_{\mathrm{birth}}$ in h277 can be explained by the same model used to describe the general decrease in velocity dispersion observed in disk galaxies from $z\sim 2-3$ to the present-day, in which the disk evolves in quasi-stable equilibrium and the ISM velocity dispersion decreases over time due to a减少气体分数。因此,我们的结果将银河系AVR的当地观察与观察到的高$ z $磁盘星系的运动学结合在一起。

Kinematic studies of disk galaxies, using individual stars in the Milky Way or statistical studies of global disk kinematics over time, provide insight into how disks form and evolve. We use a high-resolution, cosmological zoom-simulation of a Milky Way-mass disk galaxy h277 to tie together local disk kinematics and the evolution of the disk over time. The present-day stellar age-velocity relationship (AVR) of h277 is nearly identical to that of the analogous solar-neighborhood measurement in the Milky Way. A crucial element of this success is the simulation's dynamically cold multi-phase ISM, which allows young stars to form with a low velocity dispersion ($σ_{\mathrm{birth}}$$\sim 6 - 8\ \mathrm{km}\, \mathrm{s}^{-1}$) at late times. Older stars are born kinematically hotter (i.e., the disk settles over time in an "upside-down" formation scenario), and are subsequently heated after birth. The disk also grows "inside-out", and many of the older stars in the solar neighborhood at $z=0$ are present because of radial mixing. We demonstrate that the evolution of $σ_{\mathrm{birth}}$ in h277 can be explained by the same model used to describe the general decrease in velocity dispersion observed in disk galaxies from $z\sim 2-3$ to the present-day, in which the disk evolves in quasi-stable equilibrium and the ISM velocity dispersion decreases over time due to a decreasing gas fraction. Thus, our results tie together local observations of the Milky Way's AVR with observed kinematics of high $z$ disk galaxies.

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