论文标题
在Circinus Galaxy中未检测宽氢无线电重组线
Non-detection of Broad Hydrogen Radio Recombination Lines in Circinus Galaxy
论文作者
论文摘要
AGN的宽线区域（BLR）的线宽度是理解中央超大黑洞（SMBH）的关键参数。然而，由于尘土飞扬的蛋白质的晦涩，无法直接检测到II型AGN中BLR的光学重组线。无线电重组线（RRL），具有低灭绝状态，可以是II型AGN中BLR探测发射的理想示踪剂。我们对H35 $α$和H36 $α$进行了RRL观测，该观察是用Alma的Circinus Galaxy中心进行的。检测到H35 $α$和H36 $α$的狭窄组成部分，这些组件被认为主要来自核区域周围的恒星形成区域。但是，仅对宽H35 $α$和H36 $α$获得上限。由于Circinus Galaxy是最近的AGN之一，因此该乐队中Circinus Galaxy中的宽RRL未检测，这告诉我们，在具有当前设施的本地AGN中检测到宽RRL发射是无望的。一旦其后端频率覆盖范围升级到其当前功能的好几倍，它可能是直接检测II型AGN中BLR的数十倍的磁通密度，其磁通密度比毫米水平上的数十倍。
The line widths of broad line regions (BLRs) of AGNs are key parameters for understanding the central super massive black holes (SMBHs). However, due to obscuration from dusty torus, optical recombination lines from BLRs in type II AGNs can not be directly detected. Radio recombination lines (RRLs), with low extinction, can be ideal tracers to probe emission from BLRs in type II AGNs. We performed RRL observations for H35$α$ and H36$α$ toward the center of Circinus galaxy with ALMA. Narrow components of H35$α$ and H36$α$, which are thought to be mainly from star forming regions around the nuclear region, are detected. However, only upper limits are obtained for broad H35$α$ and H36$α$. Since Circinus galaxy is one of the nearest AGN, non-detection of broad RRLs in Circinus galaxy at this band tells us that it is hopeless to detect broad RRL emission in local AGNs with current facilities. Submillimetre RRLs, with flux densities that are dozens of times higher than those at the millimetre level, could be the tools to directly detect BLRs in type II AGNs with ALMA, once its backend frequency coverage has been upgraded to several times better than its current capabilities.
