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) 的一个组成部分（非热）。它们很可能在超新星爆炸产生的强烈冲击中加速，并沿着磁场线传播到ISM。由于能量损失率低，它们可以长距离运输，并且可以成为热 ISM 气体的重要能量和动量源（前提是它们可以耦合），即使在低密度区域也是如此。分析和一维计算表明，CR 对 ISM 特性具有重大影响，并有可能推动大规模资金外流。这是通过近似星系尺度的模拟表明的。然而，迄今为止，尚未对 CR 对湍流 ISM 的动力学影响进行详细的磁流体动力学 (MHD) 模拟。我们建议使用联合开发的 AMR 网格代码 FLASH 的新版本来执行此类高分辨率模拟，该版本针对 CR（十个能量仓）沿磁场线的能量相关各向异性传输进行了扩展，并考虑了绝热损耗。我们建议使用一个模块来扩展代码，该模块允许在强冲击中以从计算高效且经过良好测试的非线性扩散冲击加速半解析模型得出的速率自洽地注入 CR。借助这些强大的工具和我们在本提案中申请的两个博士职位，我们的目标是首次通过三维 MHD 模拟解决以下问题：超新星中产生的宇宙射线对湍流多核的整体动力学影响是什么？ -ISM的相结构？不同能量的宇宙射线如何通过湍流磁化ISM扩散？宇宙射线能否支持在现实结构的 ISM 中发射银河风？ CR加速度如何改变冲击结构？ CR 如何从冲击中扩散到 ISM 中？ SN 前身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超新星，CR 加速度如何变化？根据拟议研究的结果，我们很可能证明 CR 在塑造 ISM 特性方面确实发挥着比之前想象的更重要的作用。如果我们能够确认 CR 实际上可以从现实结构的 ISM 中驱动大规模星系流出，它们将成为全球参与者，在塑造 ISM 和调节所有质量和宇宙历元的恒星形成星系的形成效率方面发挥重要作用。