辐射压力限制- I。AGN的ISM中的电离气体
Radiation Pressure Confinement - I. Ionized Gas in the ISM of AGN Hosts
摘要：
分析了活动星系核辐射压对主星系光学厚气体的流体静力学效应。我们表明，在发光活动星系核，辐射压力可能会限制电离层的照明气体。辐射压力约束（RPC）有两个主要的含义。首先，电离前沿附近的气体密度为7 × 10^4 L_{i,45} r_{50} ^{-2} cm^{-3}，其中L_{i,45}是电离光度，单位为10^45 erg/s，r_{50}是气体到原子核的距离，单位为50 pc。第二，如Dopita等人所示，每个板内的电离结构的解是唯一的，与环境压力无关。我们发现，RPC密度与距离的关系可以在距原子核约10^4的动力学范围内观察到，从sub-pc到kpc，气体密度的范围为约10^8，从10^3到10^11 cm^{-3}。这种关系意味着活动星系核的辐射力可以压缩宿主星系中的巨分子云，并可能影响恒星的形成速率。RPC中独特的电离结构包括高度电离的X射线发射表面、发射日冕线的中间层和发射光学线的较低电离内层。这种结构可以解释在活动星系核附近观测到的扩展X射线和光学窄线辐射的重叠现象。我们进一步支持RPC的窄线强度和窄线宽度的预测比与现有的观测。提出了一种基于窄线宽的低光度活动星系核黑洞质量估计的新方法。
英文摘要：
We analyze the hydrostatic effect of AGN radiation pressure on optically thick gas in the host galaxy. We show that in luminous AGN, the radiation pressure likely confines the ionized layer of the illuminated gas. Radiation pressure confinement (RPC) has two main implications. First, the gas density near the ionization front is 7x10^4 L_{i,45} r_{50}^{-2} cm^{-3}, where L_{i,45} is the ionizing luminosity in units of 10^45 erg/s and r_{50} is the distance of the gas from the nucleus in units of 50 pc. Second, as shown by Dopita et al., the solution of the ionization structure within each slab is unique, independent of the ambient pressure. We show that the RPC density vs. distance relation is observed over a dynamical range of ~10^4 in distance, from sub-pc to kpc from the nucleus, and a range of ~10^8 in gas density, from 10^3 to 10^11 cm^{-3}. This relation implies that the radiative force of luminous AGN can compress giant molecular clouds in the host galaxy, and possibly affect the star formation rate. The unique ionization structure in RPC includes a highly ionized X-ray emitting surface, an intermediate layer which emits coronal lines, and a lower ionization inner layer which emits optical lines. This structure can explain the observed overlap of the extended X-ray and optical narrow line emission in nearby AGN. We further support RPC by comparing the predicted ratios of the narrow lines strength and narrow line widths with available observations. We suggest a new method, based on the narrow line widths, to estimate the black hole mass of low luminosity AGN.
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