超越简单的AGN与Chandra观测的3CRR源的统一
Beyond Simple AGN Unification with Chandra-observed 3CRR Sources
摘要：
低频射电选择发现射电明亮的星系，而不管气体和尘埃的遮蔽量。我们报告\chandra \观测一个完整的178 MHz的选择，因此方向无偏，样本的44 $0.5<z<1$ 3CRR源。样本由类星体和具有相似射电光度的窄线射电星系（NLRGs）组成，射电结构既可以作为年龄指标，也可以作为方向指标。与统一一致的是，固有的遮蔽度（通过\nh、X射线硬度比和X射线光度测量）通常随倾角而增加。然而，该样本包括在高$z$ 3CRR源中未观察到的群体：在中等倾角下使用\nh ~ $<10^{22}$ ~cm $^{-2}$观察的NLRG。多波长分析表明，这些对象有较低的$L/L_{\rm Edd}$比典型的NLRG在类似的方向。因此，取向和$L/L_{\rm Edd}$都很重要，“辐射调节的统一”提供了对样品所观察到的性质的更好解释。与$1<z<2$的3CRR样品相比，我们的低红移样品显示出更高的康普顿薄NLRG分数（45% vs. 29%），但康普顿厚的部分（20%）相似，这意味着在中等视角下康普顿薄的材料覆盖系数更大，因此环面大气层更“膨胀”。我们认为这是由于该样本中$L/L_{\rm Edd}$的范围扩展到较低的值。相比之下，在高红移下，较窄的范围和高的$L/L_{\rm Edd}$值允许取向（以及简单的统一）主导样品的观察特性。
英文摘要：
Low-frequency radio selection finds radio-bright galaxies regardless of the amount of obscuration by gas and dust. We report \chandra\ observations of a complete 178~MHz-selected, and so orientation unbiased, sample of 44 $0.5<z<1$ 3CRR sources. The sample is comprised of quasars and narrow-line radio galaxies (NLRGs) with similar radio luminosities, and the radio structure serves as both an age and an orientation indicator. Consistent with Unification, intrinsic obscuration (measured by \nh, X-ray hardness ratio, and X-ray luminosity) generally increases with inclination. However, the sample includes a population not seen in high-$z$ 3CRR sources: NLRGs viewed at intermediate inclination angles with \nh~$<10^{22}$~cm$^{-2}$. Multiwavelength analysis suggests these objects have lower $L/L_{\rm Edd}$ than typical NLRGs at similar orientation. Thus both orientation and $L/L_{\rm Edd}$ are important, and a "radiation-regulated Unification" provides a better explanation of the sample's observed properties. In comparison with the 3CRR sample at $1<z<2$, our lower-redshift sample shows a higher fraction of Compton-thin NLRGs (45\% vs.\ 29\%) but similar Compton-thick fraction (20\%), implying a larger covering factor of Compton-thin material at intermediate viewing angles and so a more "puffed-up" torus atmosphere. We posit that this is due to a range of $L/L_{\rm Edd}$ extending to lower values in this sample. In contrast, at high redshifts the narrower range and high $L/L_{\rm Edd}$ values allowed orientation (and so simple Unification) to dominate the sample's observed properties.
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