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Virialization of the Inner CGM in the FIRE Simulations and Implications for Galaxy Disks, Star Formation, and Feedback
The Astrophysical Journal ( IF 4.9 ) Pub Date : 2021-04-19 , DOI: 10.3847/1538-4357/abd776
Jonathan Stern 1 , Claude-Andr Faucher-Gigure 1 , Drummond Fielding 2 , Eliot Quataert 3 , Zachary Hafen 1 , Alexander B. Gurvich 1 , Xiangcheng Ma 3 , Lindsey Byrne 1 , Kareem El-Badry 3 , Daniel Angls-Alczar 2, 4 , T. K. Chan 5, 6 , Robert Feldmann 7 , Dušan Kereš 5 , Andrew Wetzel 8 , Norman Murray 9 , Philip F. Hopkins 10
Affiliation  

We use the FIRE-2 cosmological simulations to study the formation of a quasi-static, virial-temperature gas phase in the circumgalactic medium (CGM) at redshifts 0 < z < 5 and how the formation of this virialized phase affects the evolution of galactic disks. We demonstrate that when the halo mass crosses ∼1012 M , the cooling time of shocked gas in the inner CGM (∼0.1R vir, where R vir is the virial radius) exceeds the local free-fall time. The inner CGM then experiences a transition from on average subvirial temperatures (TT vir), large pressure fluctuations, and supersonic inflow/outflow velocities to virial temperatures (TT vir), uniform pressures, and subsonic velocities. This transition occurs when the outer CGM (∼0.5R vir) is already subsonic and has a temperature ∼T vir, indicating that the longer cooling times at large radii allow the outer CGM to virialize at lower halo masses than the inner CGM. This outside-in CGM virialization scenario is in contrast with inside-out scenarios commonly envisioned based on more idealized simulations. We demonstrate that inner CGM virialization coincides with abrupt changes in the central galaxy and its stellar feedback: the galaxy settles into a stable rotating disk, star formation transitions from “bursty” to “steady,” and stellar-driven galaxy-scale outflows are suppressed. Our results thus suggest that CGM virialization is initially associated with the formation of rotation-dominated thin galactic disks, rather than with the quenching of star formation as often assumed.



中文翻译:

FIRE 模拟中内部 CGM 的虚拟化以及对星系盘、恒星形成和反馈的影响

我们使用 FIRE-2 宇宙学模拟来研究在红移 0 < z < 5 时在环银河介质 (CGM) 中准静态、维里温度气相的形成,以及这种维里化相的形成如何影响银河系的演化磁盘。我们证明,当晕质量越过 ∼10 12 M ⊙ 时,内部 CGM 中冲击气体的冷却时间(∼0.1 R vir,其中R vir是维里半径)超过了局部自由落体时间。然后内部 CGM 经历了从平均亚病毒温度(TT vir)、大的压力波动、超音速流入/流出速度到维里温度 ( TT vir )、均匀压力和亚音速。当外部 CGM (~0.5 R vir ) 已经是亚音速并且温度~ T vir时发生这种转变,表明大半径下更长的冷却时间允许外部 CGM 在比内部 CGM 更低的光晕质量下进行虚拟化。这种由外而内的 CGM 虚拟化场景与基于更理想化的模拟通常设想的由内而外的场景形成对比。我们证明了内部 CGM 虚拟化与中央星系及其恒星反馈的突然变化相吻合:星系进入稳定的旋转盘,恒星形成从“爆发”到“稳定”转变,恒星驱动的星系尺度外流受到抑制. 因此,我们的结果表明,CGM 虚拟化最初与自转主导的薄星系盘的形成有关,而不是通常假设的与恒星形成的淬灭有关。

更新日期:2021-04-19
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