标题： 钱德拉星系团场中的强大遮蔽活动星系核 显示英文标题

标题： Powerful obscured AGN in Chandra cluster fields

摘要： 研究硬X射线背景起源的模型表明，具有最多吸积活动的源隐藏在高度遮蔽的AGN中。 我们报告了对钱德拉星系团领域中硬的偶然源的研究，这些源的流量接近源计数的拐点。 这些包括两个类型II类类星体，其测量的X射线光度大于10^{45} 尔格每秒，柱密度大于10^{23} 平方厘米^{-2}，其中一个可能是康普顿厚的。 两者都显示出红移的Fe K\alpha 线发射的迹象。 对一个高度放大且有深ISOCAM检测的源的宽波段光谱的辐射转移建模表明，存在温暖至热尘埃遮蔽着一个光度L_{紫外线}大于10^{45} 尔格每秒的类星体。 对光学暗源的多波长光谱和测光后续观测表明，这些天体位于不同红移的大型演化星系的中心，其红色光学/近红外颜色由宿主星系主导。 由于强发射特征的缺乏，尤其是红外波段，详细的源识别很困难。 我们展示了使用4米和8米望远镜获得的光学暗源的近红外光谱样本的主要结果。 通过对更硬和更亮的X射线背景源群体的研究，我们可能正在观察超大质量黑洞增长的最强烈阶段。 显示英文摘要

摘要： Models for the origin of the hard X-ray background have suggested that sources with the most accretion activity lie hidden in highly obscured AGN. We report on our study of hard, serendipitous sources in the fields of Chandra clusters with fluxes close to the turn-over in the source-counts. These include two Type II quasars with measured X-ray luminosities >10^{45} ergs per second and column-densities >10^{23} cm^{-2}, one possibly being Compton-thick. Both show indications of redshifted Fe K\alpha line emission. Radiative transfer modelling of the broad-band spectrum of a highly-magnified source with deep ISOCAM detections implies the presence of warm-to-hot dust obscuring a quasar with L_{UV}>10^{45} ergs per second. Multi-wavelength spectroscopic and photometric follow-up of the optically-faint sources suggests that these objects are found in the centres of massive evolved galaxies at a range of redshifts, with red optical / near-infrared colours dominated by the host galaxy. Detailed source identification is difficult due to the paucity of strong emission features, especially in the infrared. We present the main results from a sample of near-infrared spectra of optically-faint sources obtained with 4 m and 8 m telescopes. Through the study of the harder and brighter X-ray background source population, we are likely to be viewing the most intense phase of the growth of supermassive black holes.