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arXiv 2104.03327astro-ph.GA
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IllustrisTNG模拟中的相互作用星系--III:合并后星系中的猝灭(罕见)

Interacting galaxies in the IllustrisTNG simulations -- III: (the rarity of) quenching in post-merger galaxies

Salvatore Quai, Maan H. Hani, Sara L. Ellison, David R. Patton, Joanna Woo

摘要:

星系合并传统上是淬灭恒星形成的最佳机制之一。为了在现代宇宙学模拟的背景下测试这种范式,我们使用IllustrisTNG模拟来研究单个合并事件对猝灭的影响(即恒星形成速率至少低于恒星形成主序星3sig)。将最近合并的星系之间的猝灭速率与在红移,恒星质量,恒星形成率(SFR)、黑洞质量和环境。我们发现,在合并后的星系后代中,淬灭并不常见,只有5%的星系在合并后的5亿年内淬灭。尽管绝对速率很低,我们发现,猝灭发生在合并后的两倍的控制星系的速度。合并后1.5 Gyr的合并后代与非合并后的合并后代在统计上无法区分,这表明合并可以加速合并后的淬灭过程,这些合并后的祖先具有能够维持有效活动星系核(AGN)动力学反馈的物理条件,我们的研究结果表明,虽然淬火通常不会立即发生合并后,合并,但确实促进停止恒星形成在一些合并后。我们发现,在IllustrisTNG中,活动星系核动力学反馈的实施负责淬灭后合并,以及非后合并控制。由于释放的动能,星系经历气体损失,最终,初始气体分数低的镀锌层更倾向于淬火,淬火和星形镀锌层的主要区别因素是:在TNG中,形成星系的气体分数在fgas = 0.1处有一个尖锐的边界。

英文摘要:

Galaxy mergers are traditionally one of the favoured mechanisms for quenching star formation. To test this paradigm in the context of modern cosmological simulations, we use the IllustrisTNG simulation to investigate the impact of individual merger events on quenching (i.e. star formation rate at least 3sig below the star-forming main sequence) within 500Myr after the coalescence phase.The rate of quenching amongst recently merged galaxies is compared with a control sample that is matched in redshift, stellar mass, star formation rate (SFR), black hole mass and environment.We find quenching to be uncommon among the descendants of post-merger galaxies, with only 5% of galaxies quenching within 500 Myr after the merger.Despite this low absolute rate, we find that quenching occurs in post-mergers at twice the rate of the control galaxies.The fraction of quenched post-merger descendants 1.5 Gyr after the merger becomes statistically indistinguishable from that of non-post-mergers, suggesting that mergers could speed up the quenching process in those post-mergers whose progenitors had physical conditions able to sustain effective active galactic nuclei (AGN) kinetic feedback, thus capable of removing gas from galaxies.Our results indicate that although quenching does not commonly occur promptly after coalescence, mergers nonetheless do promote the cessation of star formation in some post-mergers. We find that, in IllustrisTNG, it is the implementation of the AGN kinetic feedback that is responsible for quenching post-mergers, as well as non-post-merger controls.As a result of the released kinetic energy, galaxies experience gas loss and eventually, they will quench.Galaxies with an initially low gas fraction show a preferable pre-disposition towards quenching.The primary distinguishing factor between quenched and star-forming galaxies is gas fraction, with a sharp boundary at fgas=0.1 in TNG.

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