A study of ten quasars with redshifts greater than four
Citations Over TimeTop 10% of 1989 papers
Abstract
In this paper we report the discovery of four quasars with redshifts in excess of four. The objects were initially detected in a low-resolution CCD grism survey. All four have strong Lyα emission lines and have brightnesses of r~20. These observations raise the number of known z>4 quasars to ten. We present CCD photometry and high signal-to-noise, moderate-resolution (25 A) spectra of all ten quasars. Nine of the objects have -27.5 < M_B_ < -25; the tenth quasar has M_B_ = -29. The spectra of these ten quasars are similar, in terms of the emission lines and shapes of the continua, to the spectra of lower-redshift quasars. There is some marginal evidence that the C IV emission lines are weaker than those found in lower-redshift quasars. The continua redward of Lyα have spectral energy indices (fnu_ is proportional to valpha^ ranging from -1.39 to -0.35; the average value of α is -0.82 +/- 0.09. The continua of all of the quasars show strong (~1 mag) depressions blueward of the Lyα emission line; this is roughly twice the value seen in quasars at a redshift of three. Spectra of three of the ten quasars possess deep (zero flux in the center of the line at this resolution) absorption features blueward of Lyα.
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