蓝色AGN样品中的电晕关系研究
Investigating the Disk-Corona Relation in a Blue AGN Sample
摘要：
我们从SDSS中编译了蓝色活动星系核样本，并研究了硬X射线与热光度之比与埃丁顿比和黑洞质量的关系。我们的样本包括240个射电宁静的塞弗特1星系和类星体。我们发现硬X射线亮度的分数（log $(L_{\rm 2-10 kev}/L_{\rm bol})$）随着爱丁顿比的增加而减小。我们还发现，硬X射线光度的分数是独立的黑洞质量的射电宁静活动星系核。log $(L_{\rm 2-10 kev}/L_{\rm bol})$随爱丁顿比的增加而减小的关系表明，X射线辐射热校正不是常数，从更大的样本支持Vasudevan和Fabian（2007）的结果。我们通过圆盘电晕蒸发/冷凝模型解释了我们的结果（Meyer et al. \cite{me200} ; Liu et al. 2002 a; Liu et al. 2007）。在这个模型的框架中，康普顿冷却在高吸积速率（以爱丁顿速率为单位）下对日冕的冷却变得有效，导致日冕气体冷凝到圆盘上。因此，当爱丁顿比增大时，日冕与盘的相对强度变弱。因此，硬X射线发射到盘发射的分数，因此到辐射热发射的分数在更高的爱丁顿比下更小。硬X射线光度与黑洞质量的独立性也可以用盘状日冕模型来解释，因为日冕结构和光度（以爱丁顿光度为单位）与黑洞的质量无关。
英文摘要：
We compile a blue AGN sample from SDSS and investigate the ratio of hard X-ray to bolometric luminosity in dependence on Eddington ratio and black hole mass. Our sample comprises 240 radio-quiet Seyfert 1 galaxies and QSOs. We find that the fraction of hard X-ray luminosity (log$(L_{\rm 2-10 kev}/L_{\rm bol})$) decreases with the increase of Eddington ratio. We also find that the fraction of hard X-ray luminosity is independent on the black hole mass for the radio-quiet AGNs. The relation of log$(L_{\rm 2-10 kev}/L_{\rm bol})$ decreasing with increasing Eddington ratio indicates that X-ray bolometric correction is not a constant, from a larger sample supporting the results of Vasudevan & Fabian (2007). We interpret our results by the disk corona evaporation/condensation model (Meyer et al. \cite{me200}; Liu et al. 2002a; Liu et al. 2007). In the frame of this model, the Compton cooling becomes efficient in cooling of the corona at high accretion rate (in units of Eddington rate), leading to condensation of corona gas to the disk. Consequently, the relative strength of corona to the disk becomes weaker at higher Eddington ratio. Therefore, the fraction of hard X-ray emission to disk emission and hence to the bolometric emission is smaller at higher Eddington ratio. The independence of the fraction of hard X-ray luminosity on the mass of the black hole can also be explained by the disk corona model since the corona structure and luminosity (in units of Eddington luminosity) are independent on the mass of black holes.
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