The host galaxies of luminous radio-quiet quasars

We present the results of a deep K-band imaging study which reveals the hos t galaxies around a sample of luminous radio-quiet quasars. The K-band imag es, obtained at UKIRT, are of sufficient quality to allow accurate modellin g of the underlying host galaxy. Initially, the basic structure of the host s is revealed using a modified CLEAN deconvolution routine optimized for th is analysis. Two of the 14 quasars are shown to have host galaxies with vio lently disturbed morphologies which cannot be modelled by smooth elliptical profiles. For the remainder of our sample, 2D models of the host and nucle ar component are fitted to the images using the chi (2) statistic to determ ine goodness of fit. Host galaxies are detected around all of the quasars. The reliability of the modelling is extensively tested, and we find the hos t luminosity to be well constrained for nine quasars. The derived average K -band absolute K-corrected host galaxy magnitude for these luminous radio-q uiet quasars is [M-K] = 25.15 +/- 0.04, slightly more luminous than an L* g alaxy. The spread of derived host galaxy luminosities is small, although th e spread of nuclear-to-host ratios is not. These host luminosities are show n to be comparable to those derived from samples of quasars of lower total luminosity, and we conclude that there is no correlation between host and n uclear luminosity for these quasars. Nuclear-to-host ratios break the lower limit previously suggested from studies of lower nuclear luminosity quasar s and Seyfert galaxies. Morphologies are less certain but, on the scales pr obed by these images, some hosts appear to be dominated by spheroids while others appear to have disc-dominated profiles.