Emerge: Empirical predictions of galaxy merger rates since z ∼ 6
Emerge: Empirical predictions of galaxy merger rates since z ∼ 6
复制标题
出现：自 z 〜 6 以来星系合并率的经验预测
DOI：
10.1093/mnras/staa3746
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
R. Somerville
中科院分区：
文献类型：
--
作者：
Joseph A O’Leary;B. Moster;T. Naab;R. Somerville
我们用星系形成的经验模型 \textsc{emerge} 来探索星系-星系合并率。平均而言，我们发现每吉里 2 美元到 20 美元之间的大质量星系 ($\log_{10}(m_{*}/M_{\odot}) \geq 10.3$) 将经历一次重大合并。我们的模型预测星系合并率，当由后代恒星质量选择时，不会按照红移幂律缩放，并且表现出明显的恒星质量和质量比依赖性。具体来说，重大合并在高质量和低红移时更为频繁。我们证明合并对于星系 $\log_{10}(m_{*}/M_{\odot}) \gtrsim 11.0$ 的恒星质量增长具有重要意义。对于质量最大的星系来说，主要合并在吸积质量分数中占主导地位，占吸积恒星总质量的比例高达 90%。我们强调，这些现象是恒星与光环质量关系的直接结果，这导致大质量星系比低质量星系更有可能经历重大合并。我们的模型产生了与最近观测结果一致的星系对分数，表现出幂律指数函数最好描述的形式。当使用已发布的观测时间尺度时，将这些对分数转换为合并率会导致与模型内在值相比的预测不准确。我们发现，假设所有观测到的对按 $z=0$ 合并，通过采用随红移线性减小的观测时间尺度，可以很好地将对分数映射到内在合并率。
We explore the galaxy-galaxy merger rate with the empirical model for galaxy formation, \textsc{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, assuming all observed pairs merge by $z=0$.
影响因子：
4.8
作者：
M. Bernardi;H. D. Sánchez;J. Brownstein;N. Drory;R. Sheth
通讯作者：
M. Bernardi;H. D. Sánchez;J. Brownstein;N. Drory;R. Sheth