辐射流体动力学中的热不稳定性：不稳定性机制，位置相关的S曲线和衰减曲线
Thermal instability in radiation hydrodynamics: instability mechanisms, position-dependent S-curves, and attenuation curves
摘要：
局部热不稳定性可以合理地解释许多不同天体物理环境中多相气体的形成，但该理论仅在辐射流体力学（RHD）方程的光学薄极限下才能得到很好的理解。在这里，我们奠定了基础，从这个限制过渡到一个完整的RHD治疗假设一个灰色的不透明度形式主义。我们考虑的情况下，气体变得热不稳定，由于硬化的辐射场时，主要的辐射过程是自由-自由冷却和康普顿加热。我们确定了两种可能发生这种情况的方式：（i）当康普顿温度随着时间的推移而增加时，通过硬X射线分量的强度或能量的上升;以及（ii）当衰减减少热分量的通量时，康普顿温度随着穿过板的深度而增加。这两种方式都可能发生在活动星系核的宽线区域，那里的气体柱可以被电离。在这种情况下，衰减是显着的，热平衡解决方案曲线成为位置依赖性，它不再足以评估在所有深度使用一个单一的平衡曲线的辐射柱的气体的稳定性。我们演示了如何分析一个新的平衡曲线-衰减曲线-为此目的，我们表明，字段的不稳定性标准，沿这条曲线的负斜率表明，恒定密度板是热不稳定的，每当气体温度随深度增加。
英文摘要：
Local thermal instability can plausibly explain the formation of multiphase gas in many different astrophysical environments, but the theory is only well understood in the optically thin limit of the equations of radiation hydrodynamics (RHD). Here we lay groundwork for transitioning from this limit to a full RHD treatment assuming a gray opacity formalism. We consider a situation where the gas becomes thermally unstable due to the hardening of the radiation field when the main radiative processes are free-free cooling and Compton heating. We identify two ways in which this can happen: (i) when the Compton temperature increases with time, through a rise in either the intensity or energy of a hard X-ray component; and (ii) when attenuation reduces the flux of the thermal component so that the Compton temperature increases with depth through the slab. Both ways likely occur in the broad line region of active galactic nuclei where columns of gas can be ionization bounded. In such instances where attenuation is significant, thermal equilibrium solution curves become position-dependent and it no longer suffices to assess the stability of an irradiated column of gas at all depths using a single equilibrium curve. We demonstrate how to analyze a new equilibrium curve -- the attenuation curve -- for this purpose, and we show that by Field's instability criterion, a negative slope along this curve indicates that constant density slabs are thermally unstable whenever the gas temperature increases with depth.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
