近似辐射输运方法在辐照圆盘研究中的可靠性
The reliability of approximate radiation transport methods for irradiated disk studies
摘要：
内容：辐照拱星盘的动力学研究需要对辐射输运进行准确的处理，例如，正确确定冷却和碎裂特性。辐射输运算法应与（磁）流体动力学一样快，以允许有效利用计算资源。方法：我们使用一个中央恒星和一个稍微张开的拱星盘的设置。我们进行模拟的光盘的中平面从tau（550 nm）= 0.1到tau（810 nm）= 1百万的光学深度范围很广。我们检查的灰色通量限制扩散（FLD）近似和灰色和频率相关的射线跟踪加FLD近似的准确性。结果：1.对于中等的光学深度，灰色近似的恒星辐射产生一个稍微热的内边缘和稍冷的磁盘在较大的半径的中平面，但在其他方面与频率相关的治疗协议。2.灰色FLD近似无法计算出一个适当的温度分布在所有制度的光学深度;比较运行的最大偏差是50%的光学薄和高达280%的光学厚的限制。对于低光学厚度，FLD方法中的各向同性假设产生径向温度斜率的过陡减小。对于更高的光学深度，FLD近似不再现的阴影后面的光学厚内边缘的拱盘，产生人工加热在更大的磁盘半径。3.与频率相关的RT +灰色FLD近似在整个光学深度范围内具有显着的准确性。结论：高精度的频率相关的混合辐射输运算法，使这种方法非常适合（磁）流体动力学研究照射拱星盘。
英文摘要：
Context: Dynamical studies of irradiated circumstellar disks require an accurate treatment of radiation transport to, for example, properly determine cooling and fragmentation properties. The radiation transport algorithm should be as fast as the (magneto-) hydrodynamics to allow for an efficient usage of computing resources. Methods: We use a setup of a central star and a slightly flared circumstellar disk. We perform simulations for a wide range of optical depths of the disk's midplane from tau(550nm) = 0.1 up to tau(810nm) = 1 million. We check the accuracy of the gray flux-limited diffusion (FLD) approximation and a gray and frequency-dependent ray-tracing plus FLD approximation. Results: 1. For moderate optical depths, a gray approximation of the stellar irradiation yields a slightly hotter inner rim and a slightly cooler midplane of the disk at larger radii, but is otherwise in agreement with the frequency-dependent treatment. 2. The gray FLD approximation fails to compute an appropriate temperature profile in all regimes of optical depth; the maximum deviations to the comparison runs are 50 percent in the optically thin and up to 280 percent in the optically thick limit. For low optical depth, the isotropic assumption within the FLD method yields a too steep decrease of the radial temperature slope. For higher optical depths, the FLD approximation does not reproduce the shadow behind the optically thick inner rim of the circumstellar disk, yielding artificial heating at larger disk radii. 3. The frequency-dependent RT + gray FLD approximation yields remarkable accuracy for the whole range of optical depths. Conclusions: The high accuracy of the frequency-dependent hybrid radiation transport algorithm makes this method ideally suited for (magneto-) hydrodynamical studies of irradiated circumstellar disks.
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