COMOVING SPACE DENSITY AND OBSCURED FRACTION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE SUBARU/XMM-NEWTON DEEP SURVEY
COMOVING SPACE DENSITY AND OBSCURED FRACTION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE SUBARU/XMM-NEWTON DEEP SURVEY
复制标题
DOI：
10.1088/0004-637x/758/1/49
复制
发表时间：
2012-08
期刊：
影响因子：
--
通讯作者：
K. Hiroi;Y. Ueda;M. Akiyama;M. Watson
中科院分区：
文献类型：
--
作者：
K. Hiroi;Y. Ueda;M. Akiyama;M. Watson
我们研究了X射线选择的发光活动星系核（AGN）的共动空间密度和在高红移（3 3与内在（去吸收和静止帧2-10 keV）的亮度LX = 1044-45 erg s−1检测在0.5-2 keV波段，包括20个和10个对象的光谱和光度红移，分别为33）的活动星系核部分。利用1/Vmax方法，我们证实了当红移大于3时，活动星系核的共动空间密度随红移的增大而减小。当与Civano等人的Chandra-COSMOS结果结合时，LX = 1044-45 erg s−1的活动星系核的密度下降可用（1 + z）−6.2 ± 0.9的幂律来表示。通过仔细考虑观测偏差，包括每个源的光子统计效应，我们还确定了在康普顿薄总体中NH > 1022 cm−2的X射线遮蔽活动星系核的比例为0.54+0.17− 0.19。这一结果与基于光学性质的2型活动星系核分数的独立测定结果一致，后者的分数为0.59 ± 0.09。将我们的结果与在局域宇宙中得到的结果相比较，我们得出结论：从z = 0到z > 3，活动星系核的遮蔽率显著增加，增加了2.5 ± 1.1倍。
We study the comoving space density of X-ray-selected luminous active galactic nuclei (AGNs) and the obscured AGN fraction at high redshifts (3 3 with intrinsic (de-absorbed and rest-frame 2–10 keV) luminosities of LX = 1044–45 erg s−1 detected in the 0.5–2 keV band, consisting of 20 and 10 objects with spectroscopic and photometric redshifts, respectively. Utilizing the 1/Vmax method, we confirm that the comoving space density of luminous AGNs decreases with redshift above z > 3. When combined with the Chandra-COSMOS result of Civano et al., the density decline of AGNs with LX = 1044–45 erg s−1 is well represented by a power law of (1 + z)−6.2 ± 0.9. We also determine the fraction of X-ray obscured AGNs with NH > 1022 cm−2 in the Compton-thin population to be 0.54+0.17− 0.19, by carefully taking into account observational biases including the effects of photon statistics for each source. This result is consistent with an independent determination of the type-2 AGN fraction based on optical properties, for which the fraction is found to be 0.59 ± 0.09. Comparing our result with that obtained in the local universe, we conclude that the obscured fraction of luminous AGNs increases significantly from z = 0 to z > 3 by a factor of 2.5 ± 1.1.