The Wide Field X-ray Telescope Mission—A Digital Sky Survey in X-rays

Sensitive surveys of the X‐ray universe have been limited to small areas of the sky due to the intrinsically small field of view of Wolter‐I X‐ray optics. High angular resolution is needed to achieve a low background per source, minimize source confusion, and distinguish point from extended objects. WFXT consists of three co‐aligned wide field X‐ray telescopes with a 1° field of view and a≲10″ (goal of 5″) angular resolution (HEW) over the full field. Total effective area at 1 keV will be >5000 cm−2. WFXT will perform three extragalactic surveys that will cover most of the sky to 100–1000 times the sensitivity of the ROSAT All Sky Survey, ≳2000 deg2 to deep Chandra or XMM‐Newton sensitivity, and ≳100 deg2 to the deepest Chandra sensitivity. WFXT will generate a legacy X‐ray dataset of a half million clusters and groups of galaxies to z≈2, also characterizing the physics of the intracluster gas for a significant fraction of them, thus providing an unprecedented data set for cosmological applications; it will detect >107 AGN to z>6, again obtaining spectra for a substantial fraction, to study the growth of supermassive black holes; it will detect >105 normal/starburst galaxies; and it will detect and characterize star formation regions across the Galaxy. WFXT is the only X‐ray survey mission that will match, in area and sensitivity, the next generation of wide‐area optical, IR and radio surveys