A Survey of z > 5.7 Quasars in the Sloan Digital Sky Survey. IV. Discovery of Seven Additional Quasars

Abstract

We present the discovery of seven quasars at z > 5.7, selected from ∼2000 deg 2 of multicolor imaging data of the Sloan Digital Sky Survey. 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 σ limit on the rest-frame equivalent width of the Lyα+N v line is 5 Å. 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 absorption gaps in Lyα. These gaps are narrower than the complete Gunn-Peterson absorption troughs observed among quasars at z > 6.2 and do not have complete Lyß absorption. © 2006. The American Astronomical Society. All rights reserved.