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arXiv 1406.4502astro-ph.HE
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钱德拉巡天中的康普顿厚活动星系核

Compton thick active galactic nuclei in Chandra surveys

Murray Brightman, Kirpal Nandra, Mara Salvato, Li-Ting Hsu, Cyprian Rangel

摘要:

我们提出的结果,从X射线光谱分析的活动星系核(AGN)在钱德拉深场南,AEGIS-XD和钱德拉宇宙调查,重点是识别和表征的最严重的模糊,康普顿厚(CT,$N_{H}>10^{24} cm^{-2}$)源。我们的样本是由3184 X射线选定的河外源,其中有一个很高的红移完成率(97.6%),并包括改进的光度红移比以前的研究。我们使用的光谱模型设计的严重模糊AGN的自我一贯包括所有主要的光谱特征的重吸收。我们确定CT源没有选择通过我们的光谱拟合方法使用X射线的颜色,验证我们的光谱拟合方法,通过模拟,并考虑到$N_{H}$的限制,我们的许多来源的低计数性质。在这些考虑之后,我们确定了总共100个CT AGN,最佳拟合$N_{H}>10^{24} cm^{-2}$和$N_{H}$在90%置信度下被限制为高于$10^{23.5} cm^{-2}$。这些源覆盖了$10^{42}-3x10^{45}$ ergs s $^{-1}$的固有$L_{X}$范围和z=0.1-4的红移范围。这个样本将使这些严重模糊的活动星系核在整个宇宙时间的特征,并确定其宇宙学意义。此外,通过使用的环面模型来测试不同的覆盖因子的情况下,并通过调查的软散射发射的列入,我们发现的证据表明,覆盖因子的遮蔽材料减少与$L_{X}$的所有红移,符合后退环面模型,这一因素增加与红移,符合增加的遮蔽分数向更高的红移。我们使$N_{H}$,$Γ$(与不确定性),观测到的X射线通量和内在的$L_{X}$在这项工作中分析的所有来源公开在一个在线目录。

英文摘要:

We present the results from an X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, AEGIS-XD and Chandra-COSMOS surveys, focussing on the identification and characterisation of the most heavily obscured, Compton thick (CT, $N_{H}>10^{24} cm^{-2}$) sources. Our sample is comprised of 3184 X-ray selected extragalactic sources, which has a high rate of redshift completeness (97.6 %), and includes improved photometric redshifts over previous studies. We use spectral models designed for heavily obscured AGN which self consistently include all major spectral signatures of heavy absorption. We identify CT sources not selected through our spectral fitting method using X-ray colours, validate our spectral fitting method through simulations, and take considerations for the constraints on $N_{H}$ given the low count nature of many of our sources. After these considerations we identify a total of 100 CT AGN with best-fit $N_{H}>10^{24} cm^{-2}$ and $N_{H}$ constrained to be above $10^{23.5} cm^{-2}$ at 90% confidence. These sources cover an intrinsic $L_{X}$ range of $10^{42}-3x10^{45}$ ergs s$^{-1}$ and a redshift range of z=0.1-4. This sample will enable characterisation of these heavily obscured AGN across cosmic time and to ascertain their cosmological significance. Furthermore, by using the torus models to test different covering factor scenarios, and by investigating the inclusion of the soft scattered emission, we find evidence that the covering factor of the obscuring material decreases with $L_{X}$ for all redshifts, consistent with the receding torus model, and that this factor increases with redshift, consistent with an increase in the obscured fraction towards higher redshifts. We make $N_{H}$, $Γ$ (with uncertainties), observed X-ray fluxes and intrinsic $L_{X}$ for all sources analysed in this work publicly available in an online catalogue.

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