Morphology of QSOs-the gridpoints of the Gaia Celestial Reference Frame

International audienceThe acronym QSO refers to the particular time in the life of giant galaxies, often elliptic ones, when the nucleus becomes extremely active fueled by matter infalling onto the accretion disk feeding the massive central black hole. But the duration and intensity of such a phase make QSOs to be treated as a class of objects, and indeed a c lass of enhanced cosmologic, astrophysical and astrometric bearings. As a consequence, even in the optical domain, the morphology of a quasar can be understood as comprehending the domineering central source, the immediate surrounding regions, the jet basis and features along the jet, and a bright host galaxy which is likely to be intensely star forming and generally speaking a lively place in itself. Morphology, and its color dependent aspects, can thus inform on the physical processes at work on a given Q SO, for example what is likeness to exhibit different time scales of variability. The ESA Gaia mission will have its fundamental reference frame formed by quasars, which are desired to be as point like as can be gathered for the sake of ensuring maximum astrometric precision and accuracy. We will present how the morphology characteristic is indicated in the Gaia Initial QSO Catalog and the related investigations. We will also outline t he Gaia extended sources methods that will be applied to all QSOs observe d, and the vast amount of information that will be made available from the mission outcomes