Near-infrared imaging of low-redshift quasar host galaxies

We present H-band images of a complete sample of 24 low-luminosity quasars selected from the Bright Quasar Survey. We detect the quasar host galaxy in at least 22 of these objects. We use a one-dimensional radial profile analysis to remove the contribution of the nucleus to the H-band light and to investigate the properties of the underlying galaxy. In most cases, the galaxy profiles are fitted better by exponential disk models than by de Vaucouleurs models. The average galaxy magnitude is 〈M_H〈; = -23.9 mag, which is approximately the H magnitude of an L* galaxy. This result argues against the quasar activity being triggered by the merger of two large galaxies. No quasar host galaxies have inclinations greater than 60°, suggesting that obscuration near the active nucleus hides many of these objects from our view; their space density could be underestimated by a factor of ∼2. We combine our results with previously published results from CCD imaging to show that the galaxies we detect are about 0.5 mag bluer in V - H than normal galaxies. Such colors can arise from a heightened level of star formation compared with normal galaxies and are consistent with these galaxies having been the sites of luminous starbursts about 10⁸ yr ago.