随时间演化的非平衡态光致电离模型及其应用

Photoionization process is ubiquitous in the universe, normally changing with time in a non-equilibrium state. Based on the latest atomic database, we propose to develop complete time-evolving photoionization models. The models prefer natural physical processes instead of constraining a lot of free parameters, which will be applied to the research of active galactic nuclei (AGN) feedback and quenching. The photoionized outflow ionized and blown out by AGN, is a significant AGN feedback mechanism having potentially influence on galaxy evolution. However, the distance from the outflow to the central black hole is hard to measure, thus the size, shape, mass of outflow are not well understood yet. Based on the time-evolving model, we can obtain the accurate distance of photoionized outflow according to the changes within the observed spectra, then investigate its origin, geometry, and mass- and energy-loss rate, and finally find out how important the outflow is for black hole accretion and galaxy evolution. The quenching of AGN makes our neighbor galaxies quieter. However, there are indications that some AGN quenched not long ago. AGN quenching time and physical state can be derived by fitting the observed spectrum with the time-evolving model, that help us better understand our living galactic surroundings.

光致电离过程存在于宇宙各个角落，并且通常处在非平衡状态随着时间变化。我们将基于最新的原子数据库，建立X射线波段下完备的随时间演化的非平衡态光致电离模型。这个模型更倾向于自然的物理演化过程，而非限定一堆的自由参数。模型将被用于AGN的外流反馈以及熄灭的研究。被AGN电离并吹出的光致电离外流是一种重要的AGN反馈形式，对星系演化有着潜在的重要影响。然而因为AGN外流到黑洞的距离难以测量，它的大小、形态和质量就都无法确定。随时间演化的模型却可以通过观测光谱发生的变化来确定距离，从而了解它的起源、几何形态以及质量能量流出率，最终了解它对黑洞吸积以及星系演化的重要性。AGN 的熄灭使得邻近星系处于较宁静的状态，但有迹象表明某些星系中AGN熄灭的时间并不久远。随时间演化的模型可以通过拟合现在的观测光谱而反推AGN熄灭的时间和物理状态，从而使我们了解生存的星系环境。

我们在2013至2015年对非平衡态光致电离机制等在星系中的影响展开研究，在基金委的支持下完成相关工作。主要取得了以下成果：1，将光致电离模型XSTAR的功能拓展到紫外波段，测量并证认了活动星系核Mrk290在X射线波段的温吸收与紫外波段的吸收源自同一外流吸收体，进一步限制了核心外流的形态与物理特征。2，发现星暴星系M82的超级风中有四分之一以上的软X射线辐射来自独特的电荷交换辐射，这帮助我们理解星系中冷热外流的相互作用方式。这种辐射机制会产生类似于光致电离的较强的OVII禁线，不过现在已可区分。3，建立了活动星系核熄灭假设下，核心热气体的非平衡光致电离的光谱随时间变化的模型。这个模型可以成功解释仙女座大星云M31的X射线光谱辐射。