We present early results from the UK ROSAT Deep and Extended Deep Surveys. A total of 240 faint X-ray sources have been detected, most of which are expected to be QSOs and Seyfert galaxies at redshifts z < 3, although normal galaxies and starburst galaxies are also present. We will use these surveys, together with our parallel VLA 20cm & 6cm radio surveys and multicolour optical CCD surveys, to determine the evolution of the faint end of the X-ray and optical luminosity functions (LF) of QSOs, study the multiwaveband emission mechanisms of QSOs, map their distribution over a ‘wedge’ of high redshift sky, and investigate the X-ray evolution of distant clusters of galaxies.
The Multiwaveband Surveys.
The ROSAT survey was performed in a region of high-latitude sky of very low, and uniform, Galactic column density (71019 cm−2), as determined by our 21cm and IRAS 100µm measurements. The deep survey reaches a limiting X-ray flux of 410−15 erg cm−2s−1 (0.5–2keV) over a 40 arcmin diameter region of sky and contains 96 faint X-ray sources. The extended survey stretches over a 4° × 40 arcmin strip starting from the position of the deep survey, with a limiting flux of 10−14 erg cm−2s−1 (0.5–2 keV).
Deep VLA radio maps at 20cm (and at 6cm in the deep survey area only) have been constructed to flux limits of 0.5 mJy on the deep survey field and 2mJy on the extended survey.