Virial shocks are suppressed in cosmic ray-dominated galaxy haloes
Virial shocks are suppressed in cosmic ray-dominated galaxy haloes
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DOI：
10.1093/mnras/stab1264
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发表时间：
2020-11
影响因子：
4.8
通讯作者：
Suoqing Ji;D. Keres̆;T. K. Chan;J. Stern;C. Hummels;P. Hopkins;E. Quataert;C. Faucher-Giguère
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作者：
Suoqing Ji;D. Keres̆;T. K. Chan;J. Stern;C. Hummels;P. Hopkins;E. Quataert;C. Faucher-Giguère
我们研究了宇宙射线(CRS)对维里激波结构的影响，使用了一套高分辨率的宇宙FIRE-2模拟程序，解释了超新星对CRs的注入。在银河系质量、低红移(z≲1−2)晕中，预计会在准流体静力平衡(有稳定的维里激波)下与缓慢冷却的气体形成“热晕”，我们的模拟没有CRS确实显示出明显的维里激波。从流入中冷凝出来的较冷的阶段成为压力限制在过密的块状中，嵌入低密度、体积填充的热气体中，体积加权冷却时间长于流入时间。因此，气体从冷的自由落体流入急剧转变为在大约维里半径(≈Rvir)处支持的热和热压，激波是准球形的。对于CRS，我们以前认为，在这个特定的质量和红移范围内的晕会形成以CR压强为主的气态晕。在这里，我们表明，当CR压强超过热压时，不存在显著的维里冲击。相反，流入的气体被CR压力梯度逐渐减速，气体相对亚音速向外甚至超过Rvir。快速冷却还保持了∼RVIR内流入气体的亚维里温度。
We study the impact of cosmic rays (CRs) on the structure of virial shocks, using a large suite of high-resolution cosmological FIRE-2 simulations accounting for CR injection by supernovae. In Milky Way-mass, low-redshift (z ≲ 1−2) haloes, which are expected to form ‘hot haloes’ with slowly cooling gas in quasi-hydrostatic equilibrium (with a stable virial shock), our simulations without CRs do exhibit clear virial shocks. The cooler phase condensing out from inflows becomes pressure confined to overdense clumps, embedded in low-density, volume-filling hot gas with volume-weighted cooling time longer than inflow time. The gas thus transitions sharply from cool free-falling inflow, to hot and thermal-pressure supported at approximately the virial radius (≈Rvir), and the shock is quasi-spherical. With CRs, we previously argued that haloes in this particular mass and redshift range build up CR-pressure-dominated gaseous haloes. Here, we show that when CR pressure dominates over thermal pressure, there is no significant virial shock. Instead, inflowing gas is gradually decelerated by the CR pressure gradient and the gas is relatively subsonic out to and even beyond Rvir. Rapid cooling also maintains subvirial temperatures in the inflowing gas within ∼Rvir.