Emission‐Line Properties ofz > 4 Quasars

We present results of a program of high signal-to-noise spectroscopy for 44QSOs at redshifts > 4 using the MMT and Keck observatories. The quasar spectracover 1100 -- 1700 A in the rest frame for sources spanning a luminosity rangeof approximately 2 orders of magnitude. Comparisons between these data andspectra of lower redshift quasars reveal a high degree of similarity, althoughdifferences are present in the profiles and the strengths of some emissionfeatures. An examination of the luminosity dependence of the emission linesreveals evidence for a weak or absent Baldwin effect among z > 4 QSOs. Wecompare measurements for objects in our sample with results from other highredshift surveys characterized by different selection techniques. Distributionsof equivalent widths for these different ensembles are consistent with a commonparent population, suggesting that our sample is not strongly biased, or in anycase, subject to selection effects that are not significantly different fromother surveys, including the Sloan Digital Sky Survey. Based on thiscomparison, we tentatively conclude that the trends identified here arerepresentative of high z QSOs. In particular, the data bolster indications ofsupersolar metallicities in these luminous, high-z sources, which supportscenarios that assume substantial star formation at epochs preceding orconcurrent with the QSO phenomena.Comment: 26 pages (incl. 9 figures), AASTeX v5.0, to appear in The Astrophysical Journa