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Astron. Astrophys. 347, 63-68 (1999)

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

Xue-Bing Wu 1,2, Norbert Bade 3 and Volker Beckmann 3

1 Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, P.R. China
2 CAS-PKU Joint Beijing Astrophysical Center, Beijing 100871, P.R. China
3 Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany

Received 25 November 1998 / Accepted 18 March 1999


X-ray luminous radio-quiet high redshift QSOs are rare and can be used for the investigation of several important astronomical questions. We have conducted a large area survey for radio-quiet high redshift QSOs in the ROSAT All-Sky Survey, from which QSO candidates are selected using the digitized objective prism spectra from the Hamburg Quasar Survey. The 22 candidates with Galactic latitudes larger than [FORMULA] were observed with the 2.16m telescope at Xinglong station of Beijing Astronomical Observatory. Among the 19 new QSOs in our sample, six are radio-quiet QSOs with redshifts larger than 1.3 and three of them have redshifts larger than 2. Thus we have doubled the number of known X-ray luminous, radio-quiet high redshift QSOs in the surveyed sky area. The distribution of [FORMULA] of radio-loud and radio-quiet QSOs in this area shows two well separated peaks. This can be taken as an evidence for different emission mechanisms of the observed X-rays in the two subgroups.

Key words: galaxies: active – galaxies: quasars: general – X-rays: galaxies

Send offprint requests to: X.-B. Wu (wuxb@class1.bao.ac.cn)

© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999