论文标题
通过爱丁顿比率探测低音AGN的结构和演变
Probing the Structure and Evolution of BASS AGN through Eddington Ratios
论文作者
论文摘要
我们使用Swift-BAT 70-月/BASS DR2调查来限制局部AGN的内在Eddington比率（\ lamedd）分布函数（log nh <= 22和22 <log nh <25）。我们从核核几何形状和时间进化方面解释了被模糊的AGN的比例。具体而言，在低爱丁顿的比率（log lamedd <-2）下，Agn含量不超过〜4的含量，反映了环核材料的覆盖率（0.8或圆环开头〜34度）。在高爱丁顿的比率（\ log lamedd> -1）下，趋势被逆转，<30％的AGN具有log NH> 22，我们建议这主要是由于在高度模糊状态下花费的时间很少。考虑到狭窄线和宽线AGN的Eddington比率分布函数，我们在定性上看到了相似的情况。为了解散高lamedd的时间和几何影响，我们探索了合理的清除场景，以使得时间加权的覆盖因子与观察到的种群比率相符。我们发现，高LAMEDD处遮盖的AGN的低比例主要是由于覆盖因子下降的速度非常迅速，而一半以上的时间则占覆盖率<10％。我们还发现，在High-Lamedd的几乎所有模糊的AGN都显示出一些宽线。我们建议这是因为耗尽的圆环的高度落在宽线区域的高度以下，从而使后者从所有视线中可见。
We constrain the intrinsic Eddington ratio (\lamEdd ) distribution function for local AGN in bins of low and high obscuration (log NH <= 22 and 22 < log NH < 25), using the Swift-BAT 70-month/BASS DR2 survey. We interpret the fraction of obscured AGN in terms of circum-nuclear geometry and temporal evolution. Specifically, at low Eddington ratios (log lamEdd < -2), obscured AGN outnumber unobscured ones by a factor of ~4, reflecting the covering factor of the circum-nuclear material (0.8, or a torus opening angle of ~ 34 degrees). At high Eddington ratios (\log lamEdd > -1), the trend is reversed, with < 30% of AGN having log NH > 22, which we suggest is mainly due to the small fraction of time spent in a highly obscured state. Considering the Eddington ratio distribution function of narrow-line and broad-line AGN from our prior work, we see a qualitatively similar picture. To disentangle temporal and geometric effects at high lamEdd, we explore plausible clearing scenarios such that the time-weighted covering factors agree with the observed population ratio. We find that the low fraction of obscured AGN at high lamEdd is primarily due to the fact that the covering factor drops very rapidly, with more than half the time is spent with < 10% covering factor. We also find that nearly all obscured AGN at high-lamEdd exhibit some broad-lines. We suggest that this is because the height of the depleted torus falls below the height of the broad-line region, making the latter visible from all lines of sight.
