March 1, 2006The Astronomical Journal461 citationsOpen Access
A Survey ofz > 5.7 Quasars in the Sloan Digital Sky Survey. IV. Discovery of Seven Additional Quasars
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Abstract
The authors present the discovery of seven quasars at z > 5. 7, selected from approx 2000 degsup 2 of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new quasars have redshifts z from 5. 79 to 6. 13. Five are selected as part of a complete flux-limited sample in the SDSS Northern Galactic Cap; two have larger photometric errors and are not part of the complete sample. One of the new quasars, SDSS J1335+3533 (z = 5. 93), exhibits no emission lines; the 3-sigma limit on the rest-frame equivalent width of Lyalpha+NV line is 5 angstrom. It is the highest redshift lineless quasar known, and could be a gravitational lensed galaxy, a BL Lac object or a new type of quasar. Two new z > 6 quasars, SDSS 1250+3130 (z = 6. 13) and SDSS J1137+3549 (z = 6. 01), show deep Gunn-Peterson troughs in Lyalpha. These troughs are narrower than those observed among quasars at z > 6. 2 and do not have complete Lybeta absorption.