球吸积在低亮度活动星系核上的秒差距尺度气体的动力学和热力学性质
Dynamical and thermal properties of the parsec-scale gases spherically accreted onto low luminous active galactic nuclei
摘要：
本文在秒差距尺度上解析地研究了光学薄气体在低光度活动星系核（LLAGN）上球形吸积时的动力学和热力学性质。下落的气体被康普顿温度为5- 15 $\times10^7$ K的中心X射线辐射。考虑了星系的辐射加热/冷却和核球恒星势。我们分析了吸积率、光度、气体温度和康普顿温度对动力学和热性质稳态解的影响。稳态解与Bondi解有明显的区别。与我们的模型相比，Bondi模型低估了吸积速率。我们给出了热稳定性和不稳定性之间的界限。边界受康普顿温度的影响很大。当康普顿温度较高时，下落的气体趋于变得热不稳定。当辐射气体发生热不稳定性时，气体变成两相（即热气体和冷气体），并且热气体可能变成流出物。这种效应可能会降低吸积速率。
英文摘要：
We analytically study the dynamical and thermal properties of the optically-thin gases at the parsec-scale when they are spherically accreted onto low luminous active galactic nuclei (LLAGNs). The falling gases are irradiated by the central X-ray radiation with the Compton temperature of 5--15$\times10^7$ K. The radiative heating/cooling and the bulge stellar potential in galaxies are taken into account. We analyze the effect of accretion rate, luminosity, gas temperature, and Compton temperature on steady solutions of dynamical and thermal properties. The steady solutions are obviously different from Bondi solution. Compared to our models, the Bondi model underestimates the accretion rate. We give the boundary between thermal stability and instability. The boundary is significantly affected by Compton temperature. When Compton temperature is higher, the falling gases tend to become thermally unstable. When thermal instability takes place in the irradiated gases, the gases become two phases (i.e. hot gases and cool gases) and the hot gases may become outflows. This effect may reduce the accretion rates.
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