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M.S. Brotherton, B. Scoggins (University of Wyoming)
Recently Vestergaard (2002) has developed an empirical method for estimating the masses of black holes in active galactic nuclei (AGNs) based on rest-frame ultraviolet spectral properties (broad C IV line width and UV continuum luminosity). The primary application of this method is for high-redshift quasars, for which the better established optical mass estimators (broad H-beta line width and optical continuum luminosity) are redshifted into the more-difficult-to-observe near-infrared. Vestergaard's empirical method is based on relatively low-luminosity quasars at low redshift and has not been explicitly tested for a significant number of high-luminosity quasars at high-redshift. We have compiled approximately 50 luminous high-z quasars for which both C IV and H-beta profiles are available and used these to estimate black hole masses. While there is significant scatter, the ratio of black hole mass estimates for the sample is consistent with unity, indicating that there is no systematic problem extrapolating C IV-based mass estimates into this region of parameter space. We find no systematic trends between either the C IV blueshift or the line width and the ratio of mass estimates. Finally, we have estimated the Eddington ratio, L/LEdd, and find that for this region of parameter space values ranging from a few percent to marginally super-Eddington. In particular, broad absorption line (BAL) quasars span the full range of Eddington ratios with no clear distinction from the other luminous quasars examined.
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Bulletin of the American Astronomical Society, 36 #2
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