标题： 活动星系核中超大质量黑洞周围的双组分混合吸积流 显示英文标题

标题： A Hybrid Two Component Accretion Flow Surrounding Supermassive Black Holes in AGN

摘要： 人们普遍认为，明亮活动星系核（AGN）中的光学/紫外和X射线辐射分别产生于吸积盘和嵌入的高温日冕中。如果物质主要以类似于双黑洞X射线双星（BHXRBs）中的冷盘状流供应，则日冕中的热电子通过对盘光子的逆康普顿散射可以有效地冷却日冕气体。因此，将这种模型应用于AGN时无法再现其观测到的X射线发射。由此通常假设部分盘吸积能量被转移到日冕中。为了避免这一假设，我们提出，由星际介质或恒星风物质的引力俘获而供给超大质量黑洞的气体在垂直方向上分布扩展。在此图景下，气体在流向黑洞的过程中部分凝结成底层的冷盘，释放出吸积能量作为X射线发射，并为盘吸积提供质量。详细的数值计算表明，X射线亮度可以达到总辐射亮度的百分之几十。对于质量供给率在埃丁顿率的0.03到0.1倍之间的情况，$\alpha_{\rm ox}$的值从0.9变化到1.2。在2-10 keV能段对应的光子指数从1.9变化到2.3。这样的图景自然地扩展了低亮度AGN的模型，在低吸积率时不存在凝结现象，并且内区没有光学厚盘。 显示英文摘要

摘要： It is commonly believed that the optical/UV and X-ray emissions in luminous AGN are produced in an accretion disk and an embedded hot corona respectively. The inverse Compton scattering of disk photons by hot electrons in the corona can effectively cool the coronal gas if the mass supply is predominantly via a cool disk like flow as in BHXRBs. Thus, the application of such a model to AGNs fails to produce their observed X-ray emission. As a consequence, a fraction of disk accretion energy is usually assumed to be transferred to the corona. To avoid this assumption, we propose that gas in a vertically extended distribution is supplied to a supermassive black hole by the gravitational capture of interstellar medium or stellar wind material. In this picture, the gas partially condenses to an underlying cool disk as it flows toward the black hole, releasing accretion energy as X-ray emission and supplying mass for the disk accretion. Detailed numerical calculations reveal that the X-ray luminosity can reach a few tens of percent of the bolometric luminosity. The value of $\alpha_{\rm ox}$ varies from 0.9 to 1.2 for the mass supply rate ranging from 0.03 to 0.1 times the Eddington value. The corresponding photon index in the 2-10 keV energy band varies from 1.9 to 2.3. Such a picture provides a natural extension of the model for low luminosity AGN where condensation is absent at low mass accretion rates and no optically thick disk exists in the inner region.