The impact of cosmic rays on dynamical balance and disc–halo interaction in L ⋆ disc galaxies
The impact of cosmic rays on dynamical balance and disc–halo interaction in L ⋆ disc galaxies
复制标题
宇宙射线对 L 盘星系动态平衡和盘晕相互作用的影响
DOI：
10.1093/mnras/stac2236
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发表时间：
2022
影响因子：
4.8
通讯作者：
Faucher-Giguère, Claude-André
中科院分区：
文献类型：
--
作者：
Chan, T. K.;Kereš, Dušan;Gurvich, Alexander B.;Hopkins, Philip F.;Trapp, Cameron;Ji, Suoqing;Faucher-Giguère, Claude-André
宇宙射线 (CR) 是星际介质中的重要组成部分，但它们对盘-晕界面（距盘<10 kpc）动力学的影响仍不清楚。我们利用红移 z∼ 0 处晚型 L⋆星系的高分辨率 FIRE-2 宇宙学模拟来研究 CR 对圆盘上方气体的影响。我们比较了有和没有 CR 反馈的运行（具有恒定各向异性扩散 κ∥∼ 3 × 1029cm2s−1 和流）。我们的模拟捕获了相关的盘-光环相互作用，包括流出、流入和银河喷泉。所有运行中的平面外气体都满足动态平衡，其中总压平衡了上覆气体的重量。虽然来自非均匀运动（≳1 kpc 尺度）的动压力在中平面中占主导地位，但热压力和体积压力（或 CR 压力，如果包括的话）在大高度上占据主导地位。我们发现，通过 CR 反馈，(1) 温暖的 (~104K) 气体被 CR 缓慢加速； (2)热(>5×105K)气标高度受到抑制； (3) 温热 (2 × 104–5 × 105K) 介质成为盘-晕界面中体积填充最多的相。我们开发了一种低红移L⋆星系中近盘气体动力学的新颖概念模型：通过CR，盘-晕界面充满了CR驱动的暖风和热超级气泡，这些气泡传播到环星系介质中，其中一小部分落回盘。如果没有 CR，热超级气泡的大部分流出物都会被现有的热晕和重力所捕获，因此它们通常会形成银河喷泉。
Cosmic rays (CRs) are an important component in the interstellar medium, but their effect on the dynamics of the disc–halo interface (<10 kpc from the disc) is still unclear. We study the influence of CRs on the gas above the disc with high-resolution FIRE-2 cosmological simulations of late-typeL⋆ galaxies at redshiftz∼ 0. We compare runs with and without CR feedback (with constant anisotropic diffusion κ∥∼ 3 × 1029cm2s−1and streaming). Our simulations capture the relevant disc–halo interactions, including outflows, inflows, and galactic fountains. Extra-planar gas in all of the runs satisfiesdynamical balance, where total pressure balances the weight of the overlying gas. While the kinetic pressure from non-uniform motion (≳1 kpc scale) dominates in the mid-plane, thermal and bulk pressures (or CR pressure if included) take over at large heights. We find that with CR feedback, (1) the warm (∼104K) gas is slowly accelerated by CRs; (2) the hot (>5 × 105K) gas scale height is suppressed; (3) the warm-hot (2 × 104–5 × 105K) medium becomes the most volume-filling phase in the disc–halo interface. We develop a novel conceptual model of the near-disc gas dynamics in low-redshiftL⋆ galaxies: with CRs, the disc–halo interface is filled with CR-driven warm winds and hot superbubbles that are propagating into the circumgalactic medium with a small fraction falling back to the disc. Without CRs, most outflows from hot superbubbles are trapped by the existing hot halo and gravity, so typically they form galactic fountains.