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Updated: Jul 28, 2026

Measurement of X-ray Beam Coherence along Multiple Directions Using 2-D Checkerboard Phase Grating
Published on: October 11, 2016
The cosmic history of the X-ray background
1Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706, USA. barger@astro.wisc.edu
Abstract:
The Chandra and XMM-Newton X-ray observatories have detected obscured active galactic nuclei (AGN) and almost fully resolved the X-ray background into discrete sources. Ground-based observations of the X-ray sources enable the reconstruction of the history of supermassive black hole accretion from the earliest times to the present. A dramatic cosmic downsizing of AGN luminosities is seen at recent times. Correspondingly, the production rate of the AGN radiation drops rapidly, and the dominant period of supermassive black hole production is seen to be at redshifts near z = 1.
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