VLT/ISAAC spectra of the Hβ region in intermediate-redshift quasars II.: Black hole mass and Eddington ratio

We derive black hole masses for a sample of about 300 AGNs in the redshift range 0 < z < 2.5. We use the same virial velocity measure (FWHM H beta(BC)) for all sources which represents a significant improvement over previous studies. We review methods and caveats for determining AGN black hole masses via the virial assumption for motions in the gas producing low ionization broad emission lines. We derive a corrected FWHM(H beta(BC)) measure for the broad component of H-beta that better estimates the virialized line emitting component by comparing our FWHM measures with a sample of reverberated sources with H beta radial velocity dispersion measures. We also consider the FWHM of the FeII gimel 4570 blend as a potential alternative velocity estimator. We find a range of black hole mass between log M-BH similar to 6.0-10.0, where M-BH is in solar masses. Estimates using corrected FWHM(H beta), as well as FWHM(FeII) measures, reduce the number of sources with log M-BH > 9.5 and suggest that extremely large M-BH values (log M-BH greater than or similar to 10) may not be realistic. Derived L/L-Edd values show no evidence for a significant population of super-Eddington radiators especially after correction is made for sources with extreme orientation to our line of sight. Sources with FWHM(H beta(BC)) less than or similar to 4000 km s(-1) show systematically higher L/L-Edd and lower MBH values than broader lined AGNs (including almost all radio-loud sources).