论文标题
高红移的超级质量黑洞有望被其大型宿主星系的恒星媒体遮盖
Supermassive Black Holes at High Redshift are Expected to be Obscured by their Massive Host Galaxies' Inter Stellar Medium
论文作者
论文摘要
我们结合了对大量（$ m _*> 10^{10} \; m _ {\ odot} $）星系的大量（$ m _*> 10^{10} \; m _*> 10^{\ odot} $）的结果，以表明其恒星间介质（ISM）的圆柱密度迅速增加朝着早期的宇宙epochs。我们的分析包括来自ASPEC和高山大程序的对象，以及$ z \ sim 6 $ QSO主机的个人观察。当考虑非探测和选择效果的校正时，我们发现大型星系群体的ISM的中间表面密度随$ \ sim（1+z）^{3.3} $演变而来。这意味着，$ z> 3 $星系的ISM柱密度通常比本地大100美元$> 100 $，并且可能达到$ z \ gtrsim6 $的compton-thick的值。值得注意的是，从X射线观测值$ z \ gtrsim2 $中的X射线观测值中，ISM柱密度的中值是相同的顺序。 我们开发了一个简单的分析模型，用于星系中ISM云的空间分布，当将ISM云在主机尺度上添加到PC尺度透明核材料（所谓的“圆环”）中时，估算了主动核的总覆盖率。该模型包括具有大小，质量和表面密度分布的云，还允许使用红移（$σ_{c，*} \ propto（1+z）^γ$的特征性云表面密度演变。我们表明，对于$γ= 2 $，这种模型成功地重现了在深X射线调查中通常观察到的遮盖的AGN分数的增加，这是当考虑不同的吸收阈值和AGN亮度时。 我们的结果表明，早期宇宙中80-90％的超质量黑洞（$ z> 6-8 $）隐藏在我们的主机中的ISM。 [简略]
We combine results from deep ALMA observations of massive ($M_*>10^{10}\;M_{\odot}$) galaxies at different redshifts to show that the column density of their inter stellar medium (ISM) rapidly increases towards early cosmic epochs. Our analysis includes objects from the ASPECS and ALPINE large programs, as well as individual observations of $z\sim 6$ QSO hosts. When accounting for non-detections and correcting for selection effects, we find that the median surface density of the ISM of the massive galaxy population evolves as $\sim(1+z)^{3.3}$. This means that the ISM column density towards the nucleus of a $z>3$ galaxy is typically $>100$ times larger than locally, and it may reach values as high as Compton-thick at $z\gtrsim6$. Remarkably, the median ISM column density is of the same order of what is measured from X-ray observations of large AGN samples already at $z\gtrsim2$. We develop a simple analytic model for the spatial distribution of ISM clouds within galaxies, and estimate the total covering factor towards active nuclei when obscuration by ISM clouds on the host scale is added to that of pc-scale circumnuclear material (the so-called 'torus'). The model includes clouds with a distribution of sizes, masses, and surface densities, and also allows for an evolution of the characteristic cloud surface density with redshift, $Σ_{c,*}\propto(1+z)^γ$. We show that, for $γ=2$, such a model successfully reproduces the increase of the obscured AGN fraction with redshift that is commonly observed in deep X-ray surveys, both when different absorption thresholds and AGN luminosities are considered. Our results suggest that 80-90\% of supermassive black holes in the early Universe ($z>6-8$) are hidden to our view, primarily by the ISM in their hosts. [abridged]
