Morphological classification of QSOs in the SDSS DR7 population

International audienceThe luminosity of the central part of QSOs may surpass that of the entire host galaxy by two or three orders of magnitude. This is certainly true among the most extreme objects, and for that reason their host galaxy study has been limited to a small number of cases at relatively low redshifts. But even in the case of less luminous objects, and given the point-like scale of the central region, it is possible to pinpoint the host galaxy through the analysis of compound PSF. In the past, we proceeded to the analysis of SDSS QSOs, that clearly showed the signature of the host galaxy of QSOs on a statistical basis. That study validated the method of using redder to bluer multi-color determinations of the QSO PSF relatively to the average PSF of nearby stars. The present study aims to analyse the complete 105783 SDSS DR7 population of QSOs, from their images in the five u, g, r, i, z bands and derived relative PSFs. This is a work in progress, and here we present the results concerning a representative sample of 8874 SDSS QSOs. The main results are that in the five bands there is a steady population of non-point-like objects, and that the targets morphology become less point-like towards the redder bands