arXiv 2107.071472021-07astro-ph.GA

在IllustrisTNG和它们的真实世界对应物中淬火的、膨胀主导的、但动力学冷的星系

Quenched, bulge-dominated, but dynamically cold galaxies in IllustrisTNG and their real-world counterparts

Shengdong Lu, Dandan Xu, Sen Wang, Yunchong Wang, Shude Mao, Xiaoyang Xia, Mark Vogelsberger, Lars Hernquist

备注：: 14 pages, 12 figures; accepted for publication in MNRAS
DOI：: 10.1093/mnras/stab3228

摘要：

星系的形态、运动学和恒星星族被认为是相互联系的。然而，模拟和观察都指出了其中的不匹配。在这项工作中，我们研究的性质和起源，目前淬火，膨胀为主，但动态冷星系的恒星质量范围内的$10.3\,\leqslant\,\log\,M_{\ast}/\mathrm{M_{\odot}}\,\leqslant\,11.2$在IllustrisTNG-100模拟。我们比较这些星系人口的正常恒星形成动态冷盘星系和人口的正常淬火动态热椭圆星系在相同的质量范围内。现今淬火和膨胀主导的星系（两者都是动态冷和热）的人口曾经有显着更高的恒星形成率和更平坦的形态在红移为$z\sim 2$。他们经历了更频繁的更大的质量比合并低于$z \sim 0.7$相比，他们的恒星形成盘的同行，这是负责形成他们的膨胀占主导地位的形态。动力冷的星系群（既有恒星形成又有淬灭）经历了更频繁的逆行和切向合并，特别是在$z \sim 1$以下，而动力热的椭圆星系则有更多的逆行和径向合并。这种不同的合并历史可以很好地解释这些星系冷、热动力学状态的差异。我们指出，这些动态冷和热膨胀为主的淬火人口的真实世界的对应物是快速和缓慢旋转的早型星系，分别在观测中看到，因此揭示了这两个不同的人口的早型星系的不同演化路径。

英文摘要：

Galaxy morphologies, kinematics, and stellar populations are thought to be linked to each other. However, both simulations and observations have pointed out mismatches therein. In this work, we study the nature and origin of the present-day quenched, bulge-dominated, but dynamically cold galaxies within a stellar mass range of $10.3\,\leqslant\,\log\,M_{\ast}/\mathrm{M_{\odot}}\,\leqslant\,11.2$ in the IllustrisTNG-100 Simulation. We compare these galaxies with a population of normal star-forming dynamically cold disc galaxies and a population of normal quenched dynamically hot elliptical galaxies within the same mass range. The populations of the present-day quenched and bulge-dominated galaxies (both being dynamically cold and hot) used to have significantly higher star-formation rates and flatter morphologies at redshift of $z\sim 2$. They have experienced more frequent larger mass-ratio mergers below $z \sim 0.7$ in comparison to their star-forming disc counterparts, which is responsible for the formation of their bulge-dominated morphologies. The dynamically cold populations (both being star-forming and quenched) have experienced more frequent prograde and tangential mergers especially below $z \sim 1$, in contrast to the dynamically hot ellipticals, which have had more retrograde and radial mergers. Such different merging histories can well explain the differences on the cold and hot dynamical status among these galaxies. We point out that the real-world counterparts of these dynamically cold and hot bulge-dominated quenched populations are the fast- and slow-rotating early-type galaxies, respectively, as seen in observations and hence reveal the different evolution paths of these two distinct populations of early-type galaxies.

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英文摘要：

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