Context. We present the study of a magnitude limited sample (mB ≤ 16.6 mag) of 13 late type galaxies (LTGs), observed inside the virial radius, Rvir ∼ 0.7 Mpc, of the Fornax cluster within the Fornax Deep Survey (FDS). Aims. The main objective is to use surface brightness profiles and g − i colour maps to obtain information on the internal structure of these galaxies and find signatures of the mechanisms that drive their evolution in high-density environments inside the virial radius of the cluster. Methods. By modelling galaxy isophotes, we extract the azimuthally averaged surface brightness profiles in four optical bands. We also derive g − i colour profiles, and relevant structural parameters like total magnitude and effective radius. For ten of the galaxies in this sample, we observe a clear discontinuity in their typical exponential surface brightness profiles, derive their “break radius”, and classify their disc-breaks into Type II (down-bending) or Type III (up-bending). Results. We find that Type II galaxies have bluer average (g − i) colour in their outer discs while Type III galaxies are redder. The break radius increases with stellar mass and molecular gas mass while it decreases with molecular gas-fractions. The inner and outer scale-lengths increase monotonically with absolute magnitude, as found in other works. For galaxies with CO(1-0) measurements, there is no detected cold gas beyond the break radius (within the uncertainties). In the context of morphological segregation of LTGs in clusters, we also find that, in Fornax, galaxies with morphological type 5 <  T ≤ 9 (∼60% of the sample) are located beyond the high-density, ETG-dominated regions, however there is no correlation between T and the disc-break type. We do not find any correlation between the average (g − i) colours and cluster-centric distance, but the colour-magnitude relation holds true. Conclusions. The main results of this work suggest that the disc-breaks of LTGs inside the virial radius of the Fornax cluster seem to have arisen through a variety of mechanisms (e.g. ram-pressure stripping, tidal disruption), which is evident in their outer-disc colours and the absence of molecular gas beyond their break radius in some cases. This can result in a variety of stellar populations inside and outside the break radii.

We present the Virgo Environment Traced in CO (VERTICO) survey, a new effort to map 12 CO (2-1), 13 CO (2-1), and C 18 O (2-1) in 51 Virgo Cluster galaxies with the Atacama Compact Array, part of the Atacama Large Millimeter/submillimeter Array. The primary motivation of VERTICO is to understand the physical mechanisms that perturb molecular gas disks, and therefore star formation and galaxy evolution, in dense environments. This first paper contains an overview of VERTICOʼs design and sample selection, 12 CO (2-1) observations, and data reduction procedures. We characterize global 12 CO (2-1) fluxes and molecular gas masses for the 49 detected VERTICO galaxies, provide upper limits for the two nondetections, and produce resolved 12 CO (2-1) data products (median resolution = 8″ ≈ 640 pc). Azimuthally averaged 12 CO (2-1) radial intensity profiles are presented along with derived molecular gas radii. We demonstrate the scientific power of VERTICO by comparing the molecular gas size-mass scaling relation for our galaxies with a control sample of field galaxies, highlighting the strong effect that radius definition has on this correlation. We discuss the drivers of the form and scatter in the size-mass relation and highlight areas for future work. VERTICO is an ideal resource for studying the fate of molecular gas in cluster galaxies and the physics of environment-driven processes that perturb the star formation cycle. Upon public release, the survey will provide a homogeneous legacy data set for studying galaxy evolution in our closest cluster.

We present the first interferometric blind HI survey of the Fornax galaxy cluster, which covers an area of 15 deg2 out to the cluster virial radius. The survey has a spatial and velocity resolution of 67″ × 95″(∼6 × 9 kpc at the Fornax cluster distance of 20 Mpc) and 6.6 km s−1 and a 3σ sensitivity of NHI ∼ 2 × 1019 cm−2 and MHI ∼ 2 × 107 M⊙, respectively. We detect 16 galaxies out of roughly 200 spectroscopically confirmed Fornax cluster members. The detections cover about three orders of magnitude in HI mass, from 8 × 106 to 1.5 × 1010 M⊙. They avoid the central, virialised region of the cluster both on the sky and in projected phase-space, showing that they are recent arrivals and that, in Fornax, HI is lost within a crossing time, ∼2 Gyr. Half of these galaxies exhibit a disturbed HI morphology, including several cases of asymmetries, tails, offsets between HI and optical centres, and a case of a truncated HI disc. This suggests that these recent arrivals have been interacting with other galaxies, the large-scale potential or the intergalactic medium, within or on their way to Fornax. As a whole, our Fornax HI detections are HI-poorer and form stars at a lower rate than non-cluster galaxies in the same M⋆ range. This is particularly evident at M⋆  ≲  109 M⊙, indicating that low mass galaxies are more strongly affected throughout their infall towards the cluster. The MHI/M⋆ ratio of Fornax galaxies is comparable to that in the Virgo cluster. At fixed M⋆, our HI detections follow the non-cluster relation between MHI and the star formation rate, and we argue that this implies that thus far they have lost their HI on a timescale ≳1−2 Gyr. Deeper inside the cluster HI removal is likely to proceed faster, as confirmed by a population of HI-undetected but H2-detected star-forming galaxies. Overall, based on ALMA data, we find a large scatter in H2-to-HI mass ratio, with several galaxies showing an unusually high ratio that is probably caused by faster HI removal. Finally, we identify an HI-rich subgroup of possible interacting galaxies dominated by NGC 1365, where pre-processing is likely to have taken place.

We present the first results of the ALMA Fornax Cluster Survey (AlFoCS): a complete ALMA survey of all members of the Fornax galaxy cluster that were detected in HI or in the far infrared with Herschel. The sample consists of a wide variety of galaxy types, ranging from giant ellipticals to spiral galaxies and dwarfs, located in all (projected) areas of the cluster. It spans a mass range of 10 ∼8.5−11 M . The CO(1-0) line was targeted as a tracer for the cold molecular gas, along with the associated 3 mm continuum. CO was detected in 15 of the 30 galaxies observed. All 8 detected galaxies with stellar masses below 3 × 10 9 M have disturbed molecular gas reservoirs, only 7 galaxies are regular/undisturbed. This implies that Fornax is still a very active environment, having a significant impact on its members. Both detections and non-detections occur at all projected locations in the cluster. Based on visual inspection, and the detection of molecular gas tails in alignment with the direction of the cluster centre, in some cases ram pressure stripping is a possible candidate for disturbing the molecular gas morphologies and kinematics. Derived gas fractions in almost all galaxies are lower than expected for field objects with the same mass, especially for the galaxies with disturbed molecular gas, with differences of sometimes more than an order of magnitude. The detection of these disturbed molecular gas reservoirs reveals the importance of the cluster environment for even the tightly bound molecular gas phase.

In this paper we study the molecular gas content of a representative sample of 67 of the most massive early-type galaxies in the local universe, drawn uniformly from the MASSIVE survey. We present new IRAM-30m telescope observations of 30 of these galaxies, allowing us to probe the molecular gas content of the entire sample to a fixed molecular-to-stellar mass fraction of 0.1%. The total detection rate in this representative sample is 25 +5.9 −4.4 %, and by combining the MASSIVE and ATLAS 3D molecular gas surveys we find a joint detection rate of 22.4 +2.4 −2.1 %. This detection rate seems to be independent of galaxy mass, size, position on the fundamental plane, and local environment. We show here for the first time that true slow rotators can host molecular gas reservoirs, but the rate at which they do so is significantly lower than for fast-rotators. Objects with a higher velocity dispersion at fixed mass (a higher kinematic bulge fraction) are less likely to have detectable molecular gas, and where gas does exist, have lower molecular gas fractions. In addition, satellite galaxies in dense environments have ≈0.6 dex lower molecular gas-to-stellar mass ratios than isolated objects. In order to interpret these results we created a toy model, which we use to constrain the origin of the gas in these systems. We are able to derive an independent estimate of the gas-rich merger rate in the low-redshift universe. These gas rich mergers appear to dominate the supply of gas to ETGs, but stellar mass loss, hot halo cooling and transformation of spiral galaxies also play a secondary role.