Broad Emission-Line Shifts in Quasars: An Orientation Measure for Radio-Quiet Quasars?

Using a sample of 3814 quasars from the Sloan Digital Sky Survey, we confirmthat high-ionization, broad, emission lines such as CIV are significantlyblueshifted with respect to low-ionization, broad, emission lines such as MgII.CIV emission line peaks have a range of shifts from a redshift of 500 km/s toblueshifts well in excess of 2000 km/s as compared to MgII. We confirm previousresults that suggest an anti-correlation between the shift of the CIV emissionline peak and the rest equivalent width of the CIV emission line. Furthermore,using composite spectra, we are able to show that the apparent shift of the CIVemission line peak is not a shift so much as it is a lack of flux in the redwing for the composite with the largest apparent shift. This observation shouldstrongly constrain models for the broad emission line region in quasars. Theemission line blueshift and equivalent width of CIV are also discussed in lightof the Baldwin Effect and as a function of other quasar properties such asspectral index, radio and X-ray detection. We find a possible correlation withboth the radio and broad absorption line properties of the quasars that issuggestive of orientation as the cause of the CIV velocity shifts.Comment: 37 pages, 11 figures (2 color), 2 tables. AJ in press. v2: Added some references and some minor corrections from the proof