Catalog of 3 < z < 5.5 Quasar Candidates Selected among XMM-Newton Sources and Its Spectroscopic Verification

• Main Authors: Georgii Khorunzhev, Sergey Sazonov, Rodion Burenin, Maxim Eselevich
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2017-11-01
• Series: Frontiers in Astronomy and Space Sciences
• Subjects: active galactic nuclei; quasars; X-ray surveys; photometric redshifts; spectroscopy; XMM-Newton
• Online Access: http://journal.frontiersin.org/article/10.3389/fspas.2017.00037/full

We have compiled a catalog of 903 quasar candidates (including known quasars) at 3 &lt; z &lt; 5.5 selected among X-ray sources from the XMM-Newton serendipitous survey (3XMM-DR4 catalog). We used photometric SDSS, 2MASS, and WISE data to select the objects. The surface number density of objects in our sample exceeds that in the SDSS spectroscopic quasar sample at the same redshifts by a factor of 1.5. We have performed spectroscopic observations of a subsample of new quasar candidates using a new low- and medium-resolution spectrograph at the 1.6-m AZT-33IK telescope (Mondy, Russia) and demonstrated that the purity of these candidates is about 65%. We have discovered one of the most distant (z = 5.08) X-ray selected quasars.