高能光子的辐射转移：X射线和C2-Ray中的氦电离
Radiative transfer of energetic photons: X-rays and helium ionization in C2-Ray
摘要：
我们提出了一个扩展的短特征射线追踪和非平衡光子电离程序C2 Ray。新版本包括氦气的效果和改进的多频加热。这项工作的动机是能够处理更硬的电离光谱，例如在宇宙再电离期间来自类星体源的光谱。在描述实施的变化之前，我们回顾了C2-Ray的基本算法成分，其中包括对全现场（OTS）近似，二次电离和多频光电离和加热的处理。我们对来自CLOUDY的平衡解进行了一系列测试，并在Iliev等人（2006）的广泛代码比较中与C2-Ray的仅含氢解进行了比较。我们表明，完整的，耦合OTS近似比简化的，非耦合的更准确。我们发现，也与氦和多频率设置，长的时间步长（高达~10%的复合时间）仍然给出准确的结果的电离分数。另一方面，温度集的精确结果对时间步长有很强的约束。然而，这些约束的细节取决于细胞的光学深度。我们使用新版本的代码，以确认在许多再电离模拟，即氦是单独电离的氢是无处不在的假设，确实是有效的源时，恒星般的光谱。
英文摘要：
We present an extension to the short-characteristic ray-tracing and non-equilibrium photon-ionization code C2Ray. The new version includes the effects of helium and improved multi-frequency heating. The motivation for this work is to be able to deal with harder ionizing spectra, such as for example from quasar-like sources during cosmic reionization. We review the basic algorithmic ingredients of C2-Ray before describing the changes implemented, which include a treatment of the full on the spot (OTS) approximation, secondary ionization, and multi-frequency photo-ionization and heating. We performed a series of tests against equilibrium solutions from CLOUDY as well as comparisons to the hydrogen only solutions by C2-Ray in the extensive code comparison in Iliev et al. (2006). We show that the full, coupled OTS approximation is more accurate than the simplified, uncoupled one. We find that also with helium and a multi-frequency set up, long timesteps (up to ~10% of the recombination time) still give accurate results for the ionization fractions. On the other hand, accurate results for the temperature set strong constrains on the timestep. The details of these constraints depend however on the optical depth of the cells. We use the new version of the code to confirm that the assumption made in many reionization simulations, namely that helium is singly ionized everywhere were hydrogen is, is indeed valid when the sources have stellar-like spectra.
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。
