标题： 一个基于物理的框架，用于比较不同时期孤立的低质量和高质量星系对的合并时间尺度 显示英文标题

标题： A Physically Motivated Framework to Compare Merger Timescales of Isolated Low- and High-Mass Galaxy Pairs Across Cosmic Time

摘要： 孤立低质量对 ($\rm 10^8<M_*<5\times10^9\,M_{\odot}$) 在宇宙学启发的轨道上的并合时标尚未被详细研究过，尽管高mass对 ($\rm 5\times10^9<M_*<10^{11}\,M_{\odot}$) 已经得到了广泛的研究。 通常会将高mass对的相同分离标准和预期的并合时标应用于低mass系统，然而，不清楚它们的并合时标是否相似，或者它们是否会随红移以类似的方式演化。 我们使用 Illustris TNG100 模拟来量化孤立低mass和高mass主要对的并合时标作为宇宙时间的函数，并探讨不同的选择标准如何影响并合时标的质量和红移依赖性。 特别是，我们提出了一个基于缩放分离标准选择对的物理动机框架，其中对的分离按主FoF群组晕的virial半径进行缩放 ($r_{\mathrm{sep}}< 1 R_{vir}$)。 应用这些缩放的分离标准在所有红移下为两个质量尺度提供了相等的并合时标。 相反，在所有红移下对所有星系对应用静态物理分离选择会导致低mass和高mass对之间的并合率差异高达$\rm \sim 1\, Gyr$，特别是在$\rm r_{sep}<150\, kpc$的情况下。 因此，对物理分离选择的对应用相同的并合时标会导致偏差，从而系统性地高估低mass星系的并合率。 显示英文摘要

摘要： The merger timescales of isolated low-mass pairs ($\rm 10^8<M_*<5\times10^9\,M_{\odot}$) on cosmologically motivated orbits have not yet been studied in detail, though isolated high-mass pairs ($\rm 5\times10^9<M_*<10^{11}\,M_{\odot}$) have been studied extensively. It is common to apply the same separation criteria and expected merger timescales of high-mass pairs to low-mass systems, however, it is unclear if their merger timescales are similar, or if they evolve similarly with redshift. We use the Illustris TNG100 simulation to quantify the merger timescales of isolated low-mass and high-mass major pairs as a function of cosmic time, and explore how different selection criteria impact the mass and redshift dependence of merger timescales. In particular, we present a physically-motivated framework for selecting pairs via a scaled separation criteria, wherein pair separations are scaled by the virial radius of the primary's FoF group halo ($r_{\mathrm{sep}}< 1 R_{vir}$). Applying these scaled separation criteria yields equivalent merger timescales for both mass scales at all redshifts. Alternatively, static physical separation selections applied equivalently to all galaxy pairs at all redshifts leads to a difference in merger rates of up to $\rm \sim 1\, Gyr$ between low- and high-mass pairs, particularly for $\rm r_{sep}<150\, kpc$. As a result, applying the same merger timescales to physical separation-selected pairs will lead to a bias that systematically over-predicts low-mass galaxy merger rates.