自适应网格加密程序FLASH的树基解算器-- III：尘埃和气体上辐射压力和漫射源辐射转移的新方案
Tree-based solvers for adaptive mesh refinement code FLASH -- III: a novel scheme for radiation pressure on dust and gas and radiative transfer from diffuse sources
摘要：
辐射是星际介质能量学的重要贡献者，然而其输运难以数值求解。本文提出了一种新的通过后向射线追踪求解漫射源辐射转移的方法。本文着重研究了红外辐射的辐射转移和尘埃的辐射压力。新的模块\textsc{TreeRay/RadPressure}是在基于网格的MHD代码{ \sc Flash}中实现的新型辐射转移方法\textsc{TreeRay}的扩展。在\textsc{TreeRay/RadPressure}中，每一个细胞和每一个恒星粒子都是红外辐射源。我们还描述了气体，尘埃和辐射是如何通过化学网络耦合的。这使我们能够计算当地的尘埃温度在热平衡，导致显着改善了经典的灰色近似。在几个测试中，我们表明，该计划产生正确的辐射强度以及正确的动量输入的辐射压力。随后，我们应用我们的新方案来模拟大质量恒星的形成，从一个崩溃的，动荡的核心150 ${\rm M}_\odot$。我们包括电离辐射和红外辐射对核心动力学的影响。我们发现，新生的大质量恒星防止其附近的碎片由于辐射加热。随着时间的推移，灰尘和辐射温度相等，而气体温度可能由于冲击加热而更热，或者由于灰尘-气体耦合不足而更冷。与引力相比，辐射压对模拟时间尺度上恒星质量的影响并不显著。
英文摘要：
Radiation is an important contributor to the energetics of the interstellar medium, yet its transport is difficult to solve numerically. We present a novel approach towards solving radiative transfer of diffuse sources via backwards ray tracing. Here we focus on the radiative transfer of infrared radiation and the radiation pressure on dust. The new module, \textsc{TreeRay/RadPressure}, is an extension to the novel radiative transfer method \textsc{TreeRay} implemented in the grid-based MHD code {\sc Flash}. In \textsc{TreeRay/RadPressure}, every cell and every star particle is a source of infrared radiation. We also describe how gas, dust and radiation are coupled via a chemical network. This allows us to compute the local dust temperature in thermal equilibrium, leading to a significantly improvement over the classical grey approximation. In several tests, we demonstrate that the scheme produces the correct radiative intensities as well as the correct momentum input by radiation pressure. Subsequently, we apply our new scheme to model massive star formation from a collapsing, turbulent core of 150 ${\rm M}_\odot$. We include the effects of both, ionizing and infrared radiation on the dynamics of the core. We find that the newborn massive star prevents fragmentation in its proximity due to radiative heating. Over time, dust and radiation temperature equalize, while the gas temperature can be either warmer due to shock heating or colder due to insufficient dust-gas coupling. Compared to gravity, the effects of radiation pressure are insignificant for the stellar mass on the simulated time scale in this work.
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