X-ray luminous radio-quiet high redshift QSOs in the ROSAT All-Sky Survey

Astronomy & Astrophysics 347, 63 (1999)

Xue-Bing Wu [1], Norbert Bade [2], Volker Beckmann [2]

  1. Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, China
  2. Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany

Abstract

X-ray luminous radio-quiet high redshift QSOs are rare and can be used for the investigation of several important astronomical topics. We have conducted a large area survey for radio-quiet high redshift QSOs in the ROSAT All-Sky Survey using digitized objective prism spectra from the Hamburg Quasar Survey to select high redshift QSO candidates. The 22 candidates with Galactic latitudes larger than 35 deg were observed with the 2.16m telescope at Xinglong station of Beijing Astronomical Observatory. Among the 19 new QSOs in our sample, 6 radio quiet QSOs have redshifts larger than 1.3 and 3 of them have redshifts larger than 2. With this finding we have doubled the number of X-ray luminous, radio quiet high redshift QSOs in the surveyed area. The distribution of f1.4GHz/f1keV of radio-loud and radio-quiet high redshift QSOs in this area shows two well separated peaks. This can be taken as evidence for different emission mechanisms of the observed X-rays in the two subgroups.

Key words: galaxies: active -- quasars: general--X-ray: galaxies

Contact: Volker Beckmann.

Preprint (compressed PS-File, 408 Kb)

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