Using an idealized set-up, we investigate the dynamical role of cosmic rays (CRs) in the early stages of galactic outflows for galaxies of halo masses $10^{8}$, $10^{11}$ and $10^{12}$ $M_\odot$. The outflow is launched from a central region in the galactic disk where we consider three different constant star formation rates ($0.1$, $1$, and $10$ $M_{\odot}$ yr$^{-1}$) over a dynamical timescale of $50$ Myr. We determine the temperature distribution of the gas and find that CRs can reduce the temperature of the shocked gas, which is consistent with previous results. However, we show that CRs do not have any noticeable effect on the mass loading by the outflow. We find that CRs can reduce the size of the outflow, which contradicts previous claims of efficient dynamical impact of CRs; however, it is consistent with earlier theoretical models of cosmic ray driven blastwave as well as stellar wind. We discuss the dependence of our results on CR injection prescriptions and compare them with earlier studies. We conclude that in the early stages of galactic outflows the dynamical role of CRs is not important.

中文翻译：

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宇宙射线在银河外流早期的作用

使用理想化的设置，我们研究了宇宙射线 (CR) 在星系外流早期阶段的动力学作用，对于晕质量为 $10^{8}$、$10^{11}$ 和 $10^{12}$ 的星系$M_\dot$。流出是从银河盘的中心区域发射的，我们考虑了三个不同的恒定恒星形成率（$0.1$、$1$ 和 $10$$M_{\odot}$yr$^{-1}$） 50 美元的时间表 Myr。我们确定了气体的温度分布，发现 CRs 可以降低冲击气体的温度，这与之前的结果一致。然而，我们表明 CR 对流出的质量负载没有任何显着影响。我们发现 CRs 可以减少流出的规模，这与先前关于 CRs 的有效动态影响的主张相矛盾；然而，它与宇宙射线驱动的冲击波和恒星风的早期理论模型一致。我们讨论了我们的结果对 CR 注射处方的依赖性，并将它们与早期的研究进行比较。我们得出结论，在星系外流的早期阶段，CR 的动力作用并不重要。