9.3 Input data treatment
The vast majority of extragalactic sources considered here are faint ( mag). The characteristics of the windows of observations for these objects are: (707 mas 2121 mas) for the Astro Fields AF [1-9] (one dimensional windows) and (4715 mas 2121 mas) for the Sky Mapper (SM) (two dimensional window). The high resolution observations (AF) are one dimensional. They allow an accurate modelling of the central part of the objects. The low resolution windows (SM) are wider and brings information about the ‘wings’ of the profile but with a degraded resolution. Therefore one can expect the surface brightness profile fitting to best represent the central part of the sources. The extraction of 2D surface brightness profiles from Gaia data requests therefore a large number of transits over the objects and a large enough angular distribution of these so that most of the extent of the source is covered.