Rest-frame optical properties of luminous, radio-selected, broad absorption line quasars

Abstract: We have obtained IRTF/SpeX spectra of eight moderate-redshift (z=0.7-2.4), radio-selected (log R*~0.4-1.9) broad absorption line (BAL) quasars. The spectra cover the rest-frame optical band. We compare the optical properties of these quasars to those of canonically radio-quiet (log R*<1) BAL quasars at similar redshifts and to low-redshift quasars from the Palomar-Green catalog. As with previous studies of BAL quasars, we find that [OIII] 5007 is weak, and optical FeII emission is strong, a rare combination in canonically radio-loud (log R*>1) quasars. With our measurements of the optical properties, particularly the Balmer emission line widths and the continuum luminosity, we have used empirical scaling relations to estimate black hole masses and Eddington ratios. These lie in the range (0.4-2.6)x10^9 M_sun and 0.1-0.9, respectively. Despite their comparatively extreme radio properties relative to most BAL quasars, their optical properties are quite consistent with those of radio-quiet BAL quasars and dissimilar to those of radio-loud non-BAL quasars. While BAL quasars generally appear to have low values of [OIII]/FeII, an extreme of "Eigenvector 1", the Balmer line widths and Eddington ratios do not appear to significantly differ from those of unabsorbed quasars at similar redshifts and luminosities.