Optical spectroscopy of candidates for quasars at 3 < <Emphasis Type="Italic">z</Emphasis> < 5.5 from the XMM-newton X-ray survey. A distant X-ray quasar at <Emphasis Type="Italic">z</Emphasis> = 5.08 |
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| Authors: | Email author" target="_blank">G?A?KhorunzhevEmail author R?A?Burenin S?Yu?Sazonov A?L?Amvrosov M?V?Eselevich |
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| Institution: | 1.Space Research Institute,Russian Academy of Sciences,Moscow,Russia;2.Institute of Solar–Terrestrial Physics,Russian Academy of Sciences, Siberian Branch,Irkutsk,Russia |
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| Abstract: | We present the results of optical spectroscopy for 19 quasar candidates at photometric redshifts z phot ? 3, 18 of which enter into the Khorunzhev et al. (2016) catalog (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. We have performed spectroscopy for a quasi-random sample of new candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory. The spectra at AZT-33IK were taken with the new low- and medium-resolution ADAM spectrograph that was produced and installed on the telescope in 2015. Fourteen of the 18 candidates actually have turned out to be quasars; 10 of them are at spectroscopic redshifts z spec > 3. The high purity of the sample of new candidates suggests that the purity of the entire K16 catalog of quasars is probably 70–80%. One of the most distant (z spec = 5.08) optically bright (i′ ? 21) quasars ever detected in X-ray surveys has been discovered. |
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