VEGAS: a VST early-type galaxy survey V. IC 1459 group: Mass assembly history in low-density environments

Context. This paper is based on the multi-band VST Early-type GAlaxy Survey (VEGAS) with the VLT Survey Telescope (VST). We present new deep photometry of the IC 1459 group in g and r band.Aims. The main goal of this work is to investigate the photometric properties of the IC 1459 group, and to compare our results with those obtained for other galaxy groups studied in VEGAS, in order to provide an initial view of the variation of their properties as a function of the evolution of the system.Methods. For all galaxies in the IC 1459 group, we fit isophotes and extract the azimuthally averaged surface-brightness profiles, the position angle, and ellipticity profiles as a function of the semi-major axis. We also extract the average colour profile. In each band, we estimate the total magnitude, effective radius, mean colour, and total stellar mass for each galaxy in the group. We then look at the structure of the brightest galaxies and the faint features in their outskirts, considering also the intragroup component.Results. The wide field of view, long integration time, high angular resolution, and arcsec-level seeing of OmegaCAM at VST allow us to map the light distribution of IC 1459 down to a surface brightness level of 29.26 mag arcsec(-2) in g band and 28.85 mag arcsec(-2) in r band, and out to 7-10R(e), and to detect the optical counterpart of HI gas around IC 1459. We also carry out an in-depth exploration of three low-density environments and provide information to understand how galaxy and group properties change with the group evolution stage.Conclusions. Good agreement is found between our results and predictions of numerical simulations regarding the structural properties of the brightest galaxies of the groups. We suggest that the structure of the outer envelope of he brightest cluster galaxies (i.e. the signatures of past mergers and tidal interactions), the intra-group light, and the HI amount and distribution may be used as indicators of the evolutionary stage and mass assembly of galaxy groups.