GALAXY MERGERS AND DARK MATTER HALO MERGERS IN ΛCDM: MASS, REDSHIFT, AND MASS-RATIO DEPENDENCE
GALAXY MERGERS AND DARK MATTER HALO MERGERS IN ΛCDM: MASS, REDSHIFT, AND MASS-RATIO DEPENDENCE
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DOI：
10.1088/0004-637x/702/2/1005
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发表时间：
2008-11
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影响因子：
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通讯作者：
Kyle R. Stewart;J. Bullock;E. Barton;R. Wechsler
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作者：
Kyle R. Stewart;J. Bullock;E. Barton;R. Wechsler
我们采用高分辨率ΛCDM n体模拟来预测暗物质（DM）晕的合并率，并研究星系中常见的合并相关观测数据（如近对计数、星暴计数和形态扰动部分）如何可能与光度、恒星质量、合并质量比和z = 0到z = 4的红移相关。我们研究了亚晕第一次进入更大晕的虚拟半径的速度（“落入率”），以及亚晕被破坏的速度，失去了它们在落入时90%的质量（“破坏率”）。对于这两种合并率定义，我们提供了一个简单的“通用”拟合公式，描述了DM晕的合并率（暗晕质量、合并质量比和红移的函数），并继续使用数密度匹配来预测星系合并率，将晕与星系联系起来。例如，我们发现m/ m > 0.3质量比事件与典型L≤f L*星系的瞬时（毁灭）合并速率遵循简单关系dN/dt≃0.03(1 + f) Gyr−1(1 + z)2.1。尽管合并率随着红移迅速增加，但在最近的700 Myr中，只有一小部分>0.4 L*的高红移星系（z = 2时约3%）应该经历过一次大合并（m/ m > 0.3） （t 0.3），并得出结论，合并几乎肯定在传递重子和影响Lyman break星系（LBGs）的运动学特性方面起着重要作用。
We employ a high-resolution ΛCDM N-body simulation to present merger rate predictions for dark matter (DM) halos and investigate how common merger-related observables for galaxies—such as close pair counts, starburst counts, and the morphologically disturbed fraction—likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z = 0 to z = 4. We investigate both rate at which subhalos first enter the virial radius of a larger halo (the “infall rate”), and the rate at which subhalos become destroyed, losing 90% of the mass they had at infall (the “destruction rate”). For both merger rate definitions, we provide a simple “universal” fitting formula that describes our derived merger rates for DM halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density matching to associate halos with galaxies. For example, we find that the instantaneous (destruction) merger rate of m/M > 0.3 mass-ratio events into typical L ≳ f L* galaxies follows the simple relation dN/dt ≃ 0.03(1 + f) Gyr−1(1 + z)2.1. Despite the rapid increase in merger rate with redshift, only a small fraction of >0.4 L* high-redshift galaxies (∼3% at z = 2) should have experienced a major merger (m/M > 0.3) in the very recent past (t 0.3) in the previous 700 Myr and conclude that mergers almost certainly play an important role in delivering baryons and influencing the kinematic properties of Lyman break galaxies (LBGs).