Discrete diffusion Lymanαradiative transfer
Discrete diffusion Lymanαradiative transfer
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离散扩散莱曼α辐射传输
DOI：
10.1093/mnras/sty1509
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发表时间：
2017
影响因子：
4.8
通讯作者：
M. Milosavljevic
中科院分区：
文献类型：
--
作者：
Aaron Smith;B. T. Tsang;V. Bromm;M. Milosavljevic
由于其准确性和通用性，蒙特卡罗辐射传递（MCRT）已成为流行的方法在任意几何形状的Ly$\alpha$辐射传递。标准MCRT在高光学深度、扩散区遇到显著的效率障碍。已经开发了多种加速方案来提高MCRT的效率，但是来自光子包离散化的噪声仍然是一个挑战。离散扩散蒙特卡罗（DDMC）方法已成功地应用于辐射流体力学（RHD）模拟。尽管如此，所建立的框架对于谐振线传输来说并不是最佳的。受DDMC范式的启发，我们提出了一种新的扩展共振DDMC（rDDMC）在空间和频率的扩散被平等对待。我们探索我们的新方法的鲁棒性，并证明了将该方法纳入现有的Ly$\alpha$代码的性能水平。我们目前的计算加速比为$\sim 10^2$-$10^6$相对于当代MCRT实现的计划，跳过散射的核心线轮廓。这是因为rDDMC运行时与空间和频率分辨率而不是散射的数量成比例-后者对于静态介质通常为$\propto \tau_0$，或者对于核心跳过为$\propto（a \tau_0）^{2/3}$。我们预计新的前沿，在飞Ly$\alpha$辐射传输计算是可行的三维RHD。更一般地说，rDDMC是转移到任何计算要求的问题服从福克-普朗克近似的频率重新分配。
Due to its accuracy and generality, Monte Carlo radiative transfer (MCRT) has emerged as the prevalent method for Ly$\alpha$ radiative transfer in arbitrary geometries. The standard MCRT encounters a significant efficiency barrier in the high optical depth, diffusion regime. Multiple acceleration schemes have been developed to improve the efficiency of MCRT but the noise from photon packet discretization remains a challenge. The discrete diffusion Monte Carlo (DDMC) scheme has been successfully applied in state-of-the-art radiation hydrodynamics (RHD) simulations. Still, the established framework is not optimal for resonant line transfer. Inspired by the DDMC paradigm, we present a novel extension to resonant DDMC (rDDMC) in which diffusion in space and frequency are treated on equal footing. We explore the robustness of our new method and demonstrate a level of performance that justifies incorporating the method into existing Ly$\alpha$ codes. We present computational speedups of $\sim 10^2$-$10^6$ relative to contemporary MCRT implementations with schemes that skip scattering in the core of the line profile. This is because the rDDMC runtime scales with the spatial and frequency resolution rather than the number of scatterings - the latter is typically $\propto \tau_0$ for static media, or $\propto (a \tau_0)^{2/3}$ with core-skipping. We anticipate new frontiers in which on-the-fly Ly$\alpha$ radiative transfer calculations are feasible in 3D RHD. More generally, rDDMC is transferable to any computationally demanding problem amenable to a Fokker-Planck approximation of frequency redistribution.