2XMMi星表与Sloan数字巡天第7版数据的互相关
Cross-correlation of the 2XMMi catalogue with Data Release 7 of the Sloan Digital Sky Survey
摘要：
XMM-牛顿卫星的测量科学中心于2008年8月发布了2XMM目录的第一个增量版本。2XMMi拥有超过220，000个X射线源，是当时出版的最大的X射线源目录，因此构成了研究活动星系核和恒星等各类X射线发射体高能特性的前所未有的资源。斯隆数字巡天第七版的出现提供了交叉匹配两个主要巡天的机会，并将许多2XMMi源的光谱能量分布扩展到光学波段。本文提出了一种基于经典似然比估计的交叉匹配算法。该方法的优点是提供真正的概率识别，而不诉诸蒙特卡罗模拟。超过30，000个2XMMi源具有SDSS对应物，其个体识别概率高于90%。使用光谱鉴定从SDSS DR 7目录补充提取从其他目录中，我们建立了一个识别的样本，从该样本中可以分析各种类别的X射线发射体在多维参数空间中的聚集方式。我们研究了两个科学用例。在第一个例子中，我们展示了如何使用这些多波长数据来搜索新的类星体2。虽然没有具体的范围内观察到的属性，让我们来确定康普顿厚类星体，我们表明，前景要好得多的康普顿薄AGN 2，并讨论了几种可能的多参数选择策略。在第二个例子中，我们在500多颗X射线活跃恒星的样本中确认了平均X射线光谱随着X射线亮度的增加而硬化，并揭示了平均而言，X射线活跃的M星显示出比不太活跃的恒星更蓝的$g-r$颜色指数（删节）。
英文摘要：
The Survey Science Centre of the XMM-Newton satellite released the first incremental version of the 2XMM catalogue in August 2008 . With more than 220,000 X-ray sources, the 2XMMi was at that time the largest catalogue of X-ray sources ever published and thus constitutes an unprecedented resource for studying the high-energy properties of various classes of X-ray emitters such as AGN and stars. The advent of the 7th release of the Sloan Digital Sky Survey offers the opportunity to cross-match two major surveys and extend the spectral energy distribution of many 2XMMi sources towards the optical bands. We here present a cross-matching algorithm based on the classical likelihood ratio estimator. The method developed has the advantage of providing true probabilities of identifications without resorting to Monte-Carlo simulations. Over 30,000 2XMMi sources have SDSS counterparts with individual probabilities of identification higher than 90%. Using spectroscopic identifications from the SDSS DR7 catalogue supplemented by extraction from other catalogues, we build an identified sample from which the way the various classes of X-ray emitters gather in the multi dimensional parameter space can be analysed. We investigate two scientific use cases. In the first example we show how these multi-wavelength data can be used to search for new QSO2s. Although no specific range of observed properties allows us to identify Compton Thick QSO2s, we show that the prospects are much better for Compton Thin AGN2 and discuss several possible multi-parameter selection strategies. In a second example, we confirm the hardening of the mean X-ray spectrum with increasing X-ray luminosity on a sample of over 500 X-ray active stars and reveal that on average X-ray active M stars display bluer $g-r$ colour indexes than less active ones (abridged).
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