Search

We present an extension of our previous research on the early-type galaxy population of the Antlia cluster (d ~ 35 Mpc), achieving a total coverage of ~ 2.6 deg x deg and performing surface photometry for ~300 galaxies, 130 of which are new uncatalogued ones. Such new galaxies mainly fall in the low surface brightness (LSB) regime, but there are also some lenticulars (S0) which support the existence of unique functions that connect bright and dwarf galaxies in the scaling relations. We analyse the projected spatial distribution of galaxies up to a distance of ~800 kpc from NGC 3268, the adopted centre, as well as the radial velocity distribution and the correlation between galaxy colour and effective radius with the projected spatial distribution. We also obtain the luminosity function of the early-type galaxies and the distribution of stellar masses using the T1-band magnitudes and adopted mass-luminosity ratios. Additionally, we correlate the central galaxy distribution with an X-ray emission map from the literature. Based on the analysis of the radial velocities and galaxy colour distributions, we find that galaxies redder than the colour-magnitude relation (CMR) have a velocity distribution strongly concentrated towards the values of the dominant galaxies and are homogeneously distributed throughout the cluster. Those bluer than the CMR, in turn, have a much more extended radial velocity distribution and are concentrated towards the centre of the cluster. We also identify 12 candidates to ultra diffuse galaxies (UDG), that seem to be split into two families, and speculate about their origins in the context of the cluster structure., Comment: Accepted for publication in MNRAS

In order to constraint the limitations of association methods applied to galaxy surveys, we analysed the catalogue of halos at $z=0$ of a cosmological simulation, trying to reproduce the limitations that an observational survey deal with. We focused in the percolation method, usually called Friends of Friends method, commonly used in literature. The analysis was carried on the dark matter cosmological simulation MDPL2, from the Multidark project. Results point to a large fraction of contaminants for massive halos in high density environments. Thresholds in the association parameters and the subsequent analysis of observational properties can mitigate the occurrence of fake positives. The use of tests for substructures can also be efficient in particular cases., Comment: Accepted in MNRAS

The present literature does not give a satisfactory answer to the question about the nature of the "Antlia galaxy cluster". The radial velocities of galaxies found in the region around the giant ellipticals NGC 3258/3268 range from about 1000 km/s to 4000 km/s. We characterise this region and its possible kinematical and population substructure. We have obtained VLT--VIMOS multi-object spectra of the galaxy population in the inner part of the Antlia cluster and measure radial velocities for 45 potential members. We supplement our galaxy sample with literature data, ending up with 105 galaxy velocities. We find a large radial velocity dispersion for the entire sample as reported in previous papers. However, we find three groups at about 1900 km/s, 2800 km/s, and 3700 km/s, which we interpret as differences in the recession velocities rather than peculiar velocities. The high radial velocity dispersion of galaxies in the Antlia region reflects a considerable extension along the line of sight., Comment: 11 pages, 7 figures, accepted in A&A

Context: There is strong evidence that globular cluster systems (GCSs) of massive galaxies are largely assembled by infall/accretion processes. Therefore, we expect the GCSs of isolated elliptical galaxies to be poor. Alhough not completely isolated, NGC 7507 is a massive field elliptical galaxy with an apparently very low dark matter content. Aims: We determine the richness, the colour distribution, and the structural properties of the GCS of NGC 7507. Methods: We perform wide-field Washington photometry with data obtained with the MOSAIC II camera at the 4m-Blanco telescope, CTIO. Results: The GCS is very poor with S_N ~ 0.6. We identify three subpopulations with peaks at (C-T1) colours of 1.21, 1.42, and 1.72. The bluest population may represent the old, metal-poor component. This interpretation is supported by its shallow density profile. The red population is more concentrated, resembling the galaxy light. The intermediate-colour population is strongly peaked in colour and we interpret this population as the signature of a starburst, whose age depends on the metallicity, but should be quite old, since no signatures of a merger are identifiable. In addition, we find a main sequence in the stellar foreground population, which we attribute to the Sagittarius dwarf tidal stream. Conclusions: The extraordinarily poor GCS of NGC 7507, a massive elliptical galaxy, is an illustration of how important the environmental conditions are for producing rich GCSs., Comment: 9 pages, 8 figures, accepted at Astronomy & Astrophysics

We present preliminary results of the search for Ultra-compact dwarf galaxies in the central region of the Antlia cluster. This new kind of stellar system has brightness, mass and size between those observed in globular clusters and early-type dwarf galaxies, but their origin is not well understood yet., Comment: 4 pages, 5 figures, accepted for publication in 52 BAAA