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arXiv 2001.02687astro-ph.GA
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EMERGE：自$z\sim6$以来星系合并率的经验预测

EMERGE: Empirical predictions of galaxy merger rates since $z\sim6$

Joseph A. O'Leary, Benjamin P. Moster, Thorsten Naab, Rachel S. Somerville

备注：
MNRAS accepted - 23 pages, 15 figures, 3 tables
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摘要：

我们探索星系合并率与经验模型的星系形成，涌现。平均而言，我们发现，在$2$ %和$20$ %之间的大质量星系（$\log_{10}(m_{*}/M_{\odot}) \geq 10.3$）将经历一个主要的合并每Gyr。我们的模型预测星系合并率不按幂律比例与红移时，由后代恒星质量选择，并表现出明确的恒星质量和质量比的依赖。具体来说，大合并在高质量和低红移时更频繁。我们发现合并对星系$\log_{10}(m_{*}/M_{\odot}) \gtrsim 11.0$的恒星质量增长是重要的。对于质量最大的星系，主要合并占吸积质量分数的主导地位，贡献高达总吸积恒星质量的$90$ %。我们强调，这些现象是恒星晕质量关系的直接结果，这导致大质量星系比低质量星系有更高的可能性经历重大合并。我们的模型产生的星系对分数与最近的观测结果一致，表现出最好的形式描述的幂律指数函数。将这些配对分数转换为合并率会导致与使用公布的观测时间尺度时的模型内在值相比预测不准确。我们发现，对分数可以很好地映射到内在的合并率，通过采用一个观察时标，随着红移线性下降为$T_{\mathrm{obs}} = -0.36(1+z)+2.39$ [Gyr]，假设所有观察到的对合并由$z=0$。

英文摘要：

We explore the galaxy-galaxy merger rate with the empirical model for galaxy formation, Emerge. On average, we find that between $2$ per cent and $20$ per cent of massive galaxies ($\log_{10}(m_{*}/M_{\odot}) \geq 10.3$) will experience a major merger per Gyr. Our model predicts galaxy merger rates that do not scale as a power-law with redshift when selected by descendant stellar mass, and exhibit a clear stellar mass and mass-ratio dependence. Specifically, major mergers are more frequent at high masses and at low redshift. We show mergers are significant for the stellar mass growth of galaxies $\log_{10}(m_{*}/M_{\odot}) \gtrsim 11.0$. For the most massive galaxies major mergers dominate the accreted mass fraction, contributing as much as $90$ per cent of the total accreted stellar mass. We reinforce that these phenomena are a direct result of the stellar-to-halo mass relation, which results in massive galaxies having a higher likelihood of experiencing major mergers than low mass galaxies. Our model produces a galaxy pair fraction consistent with recent observations, exhibiting a form best described by a power-law exponential function. Translating these pair fractions into merger rates results in an inaccurate prediction compared to the model intrinsic values when using published observation timescales. We find the pair fraction can be well mapped to the intrinsic merger rate by adopting an observation timescale that decreases linearly with redshift as $T_{\mathrm{obs}} = -0.36(1+z)+2.39$ [Gyr], assuming all observed pairs merge by $z=0$.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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