Selected Area 57 XMM-Newton X-Ray Source Catalog

The maximum number density of Active Galactic Nuclei (AGNs), as deduced from X-ray studies, occurs at z >= 1, with lower luminosity objects peaking at smaller redshifts....通过X射线研究推导得出的活动星系核（Active Galactic Nuclei，AGNs）的最大数密度出现在红移z≥1的区间，而光度较低的天体则在更小的红移处达到数密度峰值。