论文标题
银河系旅行速度对本地组动态质量估计的含义
Implications of the Milky Way travel velocity for dynamical mass estimates of the Local Group
论文作者
论文摘要
本地群体(LG)的总质量是一个基本数量,它可以解释其组成星系的轨道并将LG放置在宇宙学的环境中。允许直接推断总质量的少数方法之一是“定时参数”,它在平衡中对银河系(MW)和M31的相对轨道进行建模。 MW本身不处于平衡状态,这是其合并历史的副产品,包括最近的LMC围围通道,并且最近的工作发现,MW磁盘正在以$ \ sim 32〜 {\ rm km km}〜{\ rm km}〜{\ rm s}^{\ rm s}^{-1} $的下限“旅行速度”移动。以前的定时参数测量试图解释这种非平衡状态,但已限于特定LMC影响的理论预测。在本文中,我们使用M31最近的运动学测量值进行了几种不同的汇编来量化行进速度对回收的LG质量估计的影响。我们发现,与静态MW光环相比,将旅行速度的测量值降低了10--12 \%。具有更遥远的示踪剂的行进速度的测量值可能会产生更大的值,这将进一步降低推断的LG质量。因此,新测得的行进速度直接意味着与具有静态MW光晕的模型相比,LG质量较低,并且必须在局部体积的将来的动力学研究中考虑。
The total mass of the Local Group (LG) is a fundamental quantity that enables interpreting the orbits of its constituent galaxies and placing the LG in a cosmological context. One of the few methods that allows inferring the total mass directly is the "Timing Argument," which models the relative orbit of the Milky Way (MW) and M31 in equilibrium. The MW itself is not in equilibrium, a byproduct of its merger history including the recent pericentric passage of the LMC, and recent work has found that the MW disk is moving with a lower bound "travel velocity" of $\sim 32~{\rm km}~{\rm s}^{-1}$ with respect to the outer stellar halo. Previous Timing Argument measurements attempt to account for this non-equilibrium state, but have been restricted to theoretical predictions for the impact of the LMC specifically. In this paper, we quantify the impact of a travel velocity on recovered LG mass estimates using several different compilations of recent kinematic measurements of M31. We find that incorporating the measured value of the travel velocity lowers the inferred LG mass by 10--12\% compared to a static MW halo. Measurements of the travel velocity with more distant tracers could yield even larger values, which would further decrease the inferred LG mass. Therefore, the newly measured travel velocity directly implies a lower LG mass than from a model with a static MW halo and must be considered in future dynamical studies of the Local Volume.