2020A&A...640A.137R

Context. We present the study of the south-west group in the Fornax cluster centred on the brightest group galaxy (BGG) Fornax A, which was observed as part of the Fornax Deep Survey (FDS). This includes the analysis of the bright group members (m_B<16mag) and the intra-group light (IGL).
Aims. The main objective of this work is to investigate the assembly history of the Fornax A group and to compare its physical quantities as a function of the environment to that of the Fornax cluster core.
Methods. For all galaxies, we extracted the azimuthally averaged surface brightness profiles in three optical bands (g, r, i) by modelling the galaxy's isophotes. We derived their colour (g - i) profiles, total magnitude, effective radius in all respective bands, stellar mass, and the break radius in the r-band. The long integration time and large covered area of the FDS allowed us to also estimate the amount ofIGL.
Results. The majority of galaxies in the Fornax A group are late-type galaxies (LTGs), spanning a range of stellar mass of 8<log(M*/M_☉)<10.5. Six out of nine LTGs show a TypeIII (up-bending) break in their light profiles, which is either suggestive of strangulation halting star formation in their outskirts or their HI-richness causing enhanced star formation in their outer-discs. Overall, we do not find any correlations between their physical properties and their group-centric distance. The estimated luminosity of theIGL is 6±2x10¹⁰L_☉ in the g-band, which corresponds to about 16% of the total light in the group.
Conclusions. The Fornax A group appears to be in an early-stage of assembly with respect to the cluster core. The environment of the Fornax A group is not as dense as that of the cluster core, with all galaxies except the BGG showing similar morphology, comparable colours and stellar masses, and TypeIII disc-breaks, without any clear trend in these properties with group-centric distances. The low amount ofIGL is also consistent with this picture, since there were no significant gravitational interactions between galaxies that modified the galaxies' structure and contributed to the build-up of theIGL. The main contribution to theIGL is from the minor merging in the outskirts of the BGG NGC 1316 and, probably, the disrupted dwarf galaxies close to the group centre.