The impact of cosmic rays on the multi-phase structure of the turbulent interstellar medium

宇宙射线对湍流星际介质多相结构的影响

• 批准号: 263067211
• 负责人: Dr. Thorsten Naab
• 金额: --
• 依托单位: Max-Planck-Institut für Astrophysik (MPA)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/263067211?language=en
• 关键词: impact; cosmic; rays; multi; phase

Cosmic rays (CR) are an integral (non-thermal) part of the interstellar medium (ISM). They are most likely accelerated in strong shocks generated by supernova explosions and propagate into the ISM along magnetic field lines. Due to the low energy loss rates they can be transported over large distances and can be a significant energy and momentum source for the thermal ISM gas (provided they can couple), also in regions of low density. Analytical and one-dimensional calculations have indicated a significant impact of CRs on the ISM properties with the potential of driving large scale outflows. This was indicated by approximate galaxy scale simulations. However, no detailed magneto-hydrodynamical (MHD) simulations of the dynamical impact of CRs on the turbulent ISM have been performed so far. We propose to perform such high-resolution simulations with a jointly developed novel version of the AMR grid code FLASH extended for the energy dependent anisotropic transport of CRs (ten energy bins) along magnetic field lines and taking into account adiabatic losses. We propose to extend the code with a module that allows for the self-consistent injection of CRs in strong shocks at rates derived from a computationally efficient and well tested semi-analytical model for non-linear diffuse shock acceleration. With these powerful tools and the two PhD positions that we apply for in this proposal we aim at addressing the following questions with three-dimensional MHD simulations for the first time: What is the global dynamical impact of cosmic rays generated in supernovae on the turbulent multi-phase structure of the ISM? How do cosmic rays at different energies diffuse through the turbulent magnetized ISM? Can cosmic rays support the launching of galactic winds in a realistically structured ISM? How does CR acceleration change the shock structure? How do the CRs diffuse away from shocks into the ISM? How do ionization and stellar winds of the SN progenitor change the shock structure and the CR injection? How does the CR acceleration vary for temporally and spatially coupled SNe? With the results of the proposed study we might very well prove that CRs do play a more significant role in shaping the ISM properties than previously thought. If we can confirm that CRs can actually drive large scale galactic outflows from a realistically structured ISM they will become a global player with a major role for shaping the ISM and regulating the formation efficiency of star forming galaxies at all masses and cosmic epochs.

宇宙射线（CR）是星际介质（ISM）的一个整体（非热）部分。它们很可能在超新星爆炸产生的强烈冲击中加速，并沿着磁力线传播到ISM中。由于能量损失率低，它们可以长距离传输，并且可以成为热ISM气体的重要能量和动量来源（如果它们可以耦合），也可以在低密度区域。分析和一维计算表明，CRs对ISM属性有重大影响，有可能推动大规模外流。这是由近似星系尺度的模拟表明的。然而，到目前为止，还没有详细的磁流体动力学（MHD）模拟cr对湍流ISM的动力学影响。我们建议使用联合开发的AMR网格代码FLASH的新版本来执行这种高分辨率模拟，该代码扩展了cr（十个能量箱）沿磁磁线的能量依赖各向异性输运，并考虑了绝热损耗。我们建议用一个模块来扩展代码，该模块允许在强冲击中自一致地注入cr，其速率来自一个计算效率高且经过良好测试的非线性漫漫性冲击加速度半解析模型。有了这些强大的工具和我们申请的两个博士职位，我们的目标是第一次用三维MHD模拟来解决以下问题：超新星产生的宇宙射线对ISM湍流多相结构的全局动力学影响是什么？不同能量的宇宙射线如何在紊流磁化的ISM中扩散？宇宙射线能在一个现实结构的ISM中支持星系风的发射吗？CR加速如何改变冲击结构？CRs是如何从冲击扩散到ISM的？SN祖先的电离和恒星风如何改变激波结构和CR注入？对于时间和空间耦合的SNe， CR加速度是如何变化的？根据提出的研究结果，我们可能很好地证明，cr在形成ISM属性方面确实发挥了比以前认为的更重要的作用。如果我们能够证实CRs确实能够从现实结构的ISM中驱动大规模的星系外流，它们将成为一个全球性的参与者，在塑造ISM和调节所有质量和宇宙时代恒星形成星系的形成效率方面发挥重要作用。