The XMM-Newton serendipitous survey IV. Optical identification of the XMM-Newton medium sensitivity survey (XMS)
The XMM-Newton serendipitous survey IV. Optical identification of the XMM-Newton medium sensitivity survey (XMS)
复制标题
XMM-牛顿偶然调查 IV。
DOI：
10.1051/0004-6361:20077606
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发表时间：
2007
影响因子：
6.5
通讯作者：
Barcons X
中科院分区：
文献类型：
--
作者：
Barcons X
目的天空密度为~100℃的中等通量(10-14erg/cm-2s-1)的X射线源在10keV以下的各种能量下对宇宙X射线背景有相当大的贡献。本文的目的是提供在这些通量和不同X射线能量带上的X射线源群的无偏和定量描述。方法我们介绍了XMM-牛顿介质灵敏度调查(XMS)，包括在25个XMM-牛顿靶场的偶然内容中发现的总共318个X射线源。XMS由四个基本上重叠的源样品组成，分别选在软(0.5-2keV)、中间(0.5-4.5keV)、硬(2-10keV)和超硬(4.5-7.5keV)波段，其中前三个是通量受限的。在XMS采样的通量水平上，我们发现X射线天空主要由活动星系核主导。在软X射线选择的样本中，恒星的比例低于10%，而在硬选择的样本中，只有几个百分点。我们发现，在20年的流量中，对于软波段和中波段选择的X射线源，AGN总体中光学遮挡物体的比例保持不变，保持在15%-20%左右。在硬或超硬选择的样品中，活动星系核总体中被遮挡的物体的比例较大(~35-45%)，并且在类似的宽通量范围内保持不变。X射线光通量比的分布是选择带的强函数，在硬选择的样品中高值的源所占的比例较大。X射线与光通量比超过10的源主要是被遮挡的活动星系核，但也有来自非遮挡活动星系核的显著贡献。
AimsX-ray sources at intermediate fluxes (a few 10-14erg cm-2s-1) with a sky density of ~100 deg-2are responsible for a significant fraction of the cosmic X-ray background at various energies below 10 keV. The aim of this paper is to provide an unbiased and quantitative description of the X-ray source population at these fluxes and in various X-ray energy bands.MethodsWe present the XMM-Newton Medium sensitivity Survey (XMS), including a total of 318 X-ray sources found among the serendipitous content of 25 XMM-Newton target fields. The XMS comprises four largely overlapping source samples selected at soft (0.5-2 keV), intermediate (0.5-4.5 keV), hard (2-10 keV) and ultra-hard (4.5-7.5 keV) bands, the first three of them being flux-limited.ResultsWe report on the optical identification of the XMS samples, complete to 85-95%. At the flux levels sampled by the XMS we find that the X-ray sky is largely dominated by Active Galactic Nuclei. The fraction of stars in soft X-ray selected samples is below 10%, and only a few per cent for hard selected samples. We find that the fraction of optically obscured objects in the AGN population stays constant at around 15-20% for soft and intermediate band selected X-ray sources, over 2 decades of flux. The fraction of obscured objects amongst the AGN population is larger (~35-45%) in the hard or ultra-hard selected samples, and constant across a similarly wide flux range. The distribution in X-ray-to-optical flux ratio is a strong function of the selection band, with a larger fraction of sources with high values in hard selected samples. Sources with X-ray-to-optical flux ratios in excess of 10 are dominated by obscured AGN, but with a significant contribution from unobscured AGN.