Five high-redshift quasars discovered in commissioning imaging data of the Sloan Digital Sky Survey

Abstract

We report the discovery of five quasars with redshifts of 4.67-5.27 and z'-band magnitudes of 19.5-20.7 (M-B similar to -27). All were originally selected as distant quasar candidates in optical/near-infrared photometry from the Sloan Digital Sky Survey (SDSS), and most were confirmed as probable high-redshift quasars by supplementing the SDSS data with J and K measurements. The quasars possess strong, broad Ly alpha emission lines, with the characteristic sharp cutoff on the blue side produced by Ly alpha forest absorption. Three quasars contain strong, broad absorption features, and one of them exhibits very strong N v emission. The amount of absorption produced by the Lya forest increases toward higher redshift, and that in the z = 5.27 object (D-A approximate to 0.7) is consistent with a smooth extrapolation of the absorption seen in lower redshift quasars. The high luminosity of these objects relative to most other known objects at z greater than or similar to 5 makes them potentially valuable as probes of early quasar properties and of the intervening intergalactic medium.