A simple sub-grid model for cosmic ray effects on galactic scales
A simple sub-grid model for cosmic ray effects on galactic scales
复制标题
银河尺度上宇宙射线效应的简单子网格模型
DOI：
10.1093/mnras/stad976
复制
发表时间：
2023
影响因子：
4.8
通讯作者：
Kereš, Dušan
中科院分区：
文献类型：
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作者：
Hopkins, Philip F.;Butsky, Iryna S.;Ji, Suoqing;Kereš, Dušan
最近的许多数值研究认为，来自超新星(SNE)或活动星系核(AGN)的宇宙射线(CRS)可能在星系形成中发挥关键作用，特别是通过建立CR压强主导的环星系介质(CGM)。但显式CR-磁流体力学(CR-MHD)的计算成本仍然很高，目前还不清楚这些结果是否可以应用于没有显式处理磁场或解析星际介质相结构的模拟。因此，我们提出了一个特意简化的CRS“子网格”模型，它试图捕捉那些对模拟或半解析模型最感兴趣的关键定性行为，包括银河系(≳ )尺度上的一些近似CR效应，同时施加的计算开销可以忽略不计。该模型在数值上类似于最近发展的一些用于辐射反馈的子格子模型，并允许对CR扩散率和/或流动速度进行简单的常量参数化；它允许源的任意分布(与黑洞吸积率或恒星粒子SNE率或气体/星系恒星形成率成正比)，并在CRS以可忽略的损失逃离星系的极限和CRS在逃逸之前灾难性地损失大部分能量的极限(例如星爆星系)之间进行内插。在大多数程序中，数值方程都是与重力一起求解的。我们将这与显式CR-MHD模拟进行比较，并讨论(许多)子网格近似在哪里崩溃，以及是什么驱动了主要的不确定性来源。
Many recent numerical studies have argued that cosmic rays (CRs) from supernovae (SNe) or active galactic nuclei (AGNs) could play a crucial role in galaxy formation, in particular by establishing a CR-pressure-dominated circumgalactic medium (CGM). But explicit CR-magnetohydrodynamics (CR-MHD) remains computationally expensive, and it is not clear whether those results can be applied to simulations that do not explicitly treat magnetic fields or resolved interstellar medium phase structure. We therefore present an intentionally extremely simplified ‘sub-grid’ model for CRs, which attempts to capture the key qualitative behaviors of greatest interest for those interested in simulations or semi-analytical models including some approximate CR effects on galactic (≳ kpc) scales, while imposing negligible computational overhead. The model is numerically akin to some recently developed sub-grid models for radiative feedback, and allows for a simple constant parametrization of the CR diffusivity and/or streaming speed; it allows for an arbitrary distribution of sources (proportional to black hole accretion rates or star–particle SNe rates or gas/galaxy star formation rates), and interpolates between the limits where CRs escape the galaxies with negligible losses and those where CRs lose most of their energy catastrophically before escape (relevant in e.g. starburst galaxies). The numerical equations are solved trivially alongside gravity in most codes. We compare this to explicit CR-MHD simulations and discuss where the (many) sub-grid approximations break down, and what drives the major sources of uncertainty.
DOI：
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发表时间：
2002
期刊：
影响因子：
--
作者：
J. O’Brien
通讯作者：
J. O’Brien