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 (mB < 16 mag) 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 of IGL. 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 Type III (up-bending) break in their light profiles, which is either suggestive of strangulation halting star formation in their outskirts or their H I-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 the IGL is 6 ± 2 × 1010 L⊙ 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 Type III disc-breaks, without any clear trend in these properties with group-centric distances. The low amount of IGL 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 the IGL. The main contribution to the IGL is from the minor merging in the outskirts of the BGG NGC 1316 and, probably, the disrupted dwarf galaxies close to the group centre.

Context. This work is based on deep multi-band (g, r, i) data from the Fornax Deep Survey with the VLT Survey Telescope (VST). We analyse the surface brightness profiles of the 19 bright early-type galaxies (ETGs; mB ≤ 15 mag) inside the virial radius of the Fornax cluster (Rvir ∼ 0.7 Mpc), in the mass range 8 × 108 ≤ M* ≤ 1.2 × 1011 M⊙. Aims. The main aim of this work is to identify signatures of accretion onto galaxies by studying the presence of outer stellar haloes and to understand their nature and occurrence. Our analysis also provides a new and accurate estimate of the intra-cluster light inside the virial radius of Fornax. Methods. We performed multi-component fits to the azimuthally averaged surface brightness profiles available for all sample galaxies. This allows us to quantify the relative weight of all components in the galaxy structure that contribute to the total light. In addition, we derived the average g − i colours in each component identified by the fit, as well as the azimuthally averaged g − i colour profiles, to correlate them with the stellar mass of each galaxy and the location inside the cluster. Results. We find that in the most massive (1010 ≤ M ≤ 1011 M⊙) and reddest ETGs the fraction of light in, probably accreted, haloes (50%–90%) is much larger than in the other galaxies. All of these are located in the high-density region of the cluster (≤0.4Rvir ∼ 0.3 Mpc), belonging to the north-south clump (NS clump). Less massive galaxies (109 ≤ M ≤ 1010 M⊙) have an accreted mass fraction that is lower than 30%, have bluer colours, and reside in the low-density regions of the cluster. The colour profiles of the ETGs with the largest accreted mass fraction tend to flatten in the outskirts of the galaxy, that is beyond the transition radius from the central in situ to the ex situ accreted component. Inside the virial radius of the cluster (∼0.7 Mpc), the total luminosity of the intra-cluster light, compared with the total luminosity of all cluster members (bright galaxies and dwarfs), is about 34%. Conclusions. Inside the Fornax cluster there is a clear correlation between the amount of accreted material in the stellar haloes of galaxies and the density of the environment in which those galaxies reside. By comparing this quantity with theoretical predictions and previous observational estimates, there is a clear indication that the driving factor for the accretion process is the total stellar mass of the galaxy, which agrees with the hierarchical accretion scenario. Massive galaxies in the NS clump, with the largest accreted mass fractions, went through pre-processing in a group environment before this group merged with the main cluster early on. At the present epoch of the Fornax assembly history, these galaxies are the major contribution to the stellar density in the core of the cluster.

We present the final data release of the APEX low-redshift legacy survey for molecular gas (ALLSMOG), comprising CO(2-1) emission line observations of 88 nearby, low-mass (10 8.5 < M * [M ] < 10 10 ) star-forming galaxies carried out with the 230 GHz APEX-1 receiver on the APEX telescope. The main goal of ALLSMOG is to probe the molecular gas content of more typical and lower stellar mass galaxies than have been studied by previous CO surveys. We also present IRAM 30 m observations of the CO(1-0) and CO(2-1) emission lines in nine galaxies aimed at increasing the M * < 10 9 M sample size. In this paper we describe the observations, data reduction and analysis methods and we present the final CO spectra together with archival Hi 21 cm line observations for the entire sample of 97 galaxies. At the sensitivity limit of ALLSMOG, we register a total CO detection rate of 47%. Galaxies with higher M * , SFR, nebular extinction (A V ), gas-phase metallicity (O/H), and Hi gas mass have systematically higher CO detection rates. In particular, the parameter according to which CO detections and non-detections show the strongest statistical differences is the gas-phase metallicity, for any of the five metallicity calibrations examined in this work. We investigate scaling relations between the CO(1-0) line luminosity (L CO(1−0) ) and galaxy-averaged properties using ALLSMOG and a sub-sample of COLD GASS for a total of 185 sources that probe the local main sequence (MS) of star-forming galaxies and its ±0.3 dex intrinsic scatter from M * = 10 8.5 M to M * = 10 11 M . L CO(1−0) is most strongly correlated with the SFR, but the correlation with M * is closer to linear and almost comparably tight. The relation between L CO(1−0) and metallicity is the steepest one, although deeper CO observations of galaxies with A V < 0.5 mag may reveal an as much steep correlation with A V . Our results suggest that star-forming galaxies across more than two orders of magnitude in M * obey similar scaling relations between CO luminosity and the galaxy properties examined in this work. Besides SFR, the CO luminosity is likely most fundamentally linked to M * , although we note that stellar mass alone cannot explain all of the variation in CO emission observed as a function of O/H and M HI .