Impact of Cosmic-Ray Transport on Galactic Winds
Impact of Cosmic-Ray Transport on Galactic Winds
复制标题
DOI：
10.3847/1538-4357/aab26d
复制
发表时间：
2017-07
期刊：
影响因子：
--
通讯作者：
R. Farber;M. Ruszkowski;Karen Yang;E. Zweibel
中科院分区：
文献类型：
--
作者：
R. Farber;M. Ruszkowski;Karen Yang;E. Zweibel
超新星和年轻恒星产生的宇宙射线的作用最近开始在星系形成和演化的研究中受到重视，因为人们认识到宇宙射线可以有效地加速星系风。微观宇宙线输运过程是决定宇宙线风驱动效率的基础。以前的研究通过恒定的扩散系数或通过与阿尔文速度成比例的流动来模拟宇宙射线的传输。然而，在主要是冷的中性气体中，宇宙射线可以比在电离介质中传播得更快，并且有效传输可以大得多;即，宇宙射线可以与气体分离。我们进行三维磁流体力学模拟补丁的星系盘，包括宇宙射线的影响。我们的模拟包括在寒冷的中性星际介质中宇宙射线的解耦。我们发现，相比于普通的扩散宇宙射线输运的情况下，占去耦导致显着不同的风属性，如气体密度和温度，显着更广泛的宇宙射线的空间分布，和更高的风速。这些结果对X射线、γ射线和射电辐射，以及环星系介质的磁化和宇宙射线污染都有意义。
The role of cosmic rays generated by supernovae and young stars has very recently begun to receive significant attention in studies of galaxy formation and evolution due to the realization that cosmic rays can efficiently accelerate galactic winds. Microscopic cosmic-ray transport processes are fundamental for determining the efficiency of cosmic-ray wind driving. Previous studies modeled cosmic-ray transport either via a constant diffusion coefficient or via streaming proportional to the Alfvén speed. However, in predominantly cold, neutral gas, cosmic rays can propagate faster than in the ionized medium, and the effective transport can be substantially larger; i.e., cosmic rays can decouple from the gas. We perform three-dimensional magnetohydrodynamical simulations of patches of galactic disks including the effects of cosmic rays. Our simulations include the decoupling of cosmic rays in the cold, neutral interstellar medium. We find that, compared to the ordinary diffusive cosmic-ray transport case, accounting for the decoupling leads to significantly different wind properties, such as the gas density and temperature, significantly broader spatial distribution of cosmic rays, and higher wind speed. These results have implications for X-ray, γ-ray, and radio emission, and for the magnetization and pollution of the circumgalactic medium by cosmic rays.