Galaxy populations in the Antlia cluster – I. Photometric properties of early-type galaxies

Abstract

We present the first colour–magnitude relation (CMR) of early‐type galaxies in the central region of the Antlia cluster, obtained from CCD wide‐field photometry in the Washington photometric system. Integrated (C−T1) colours, T1 magnitudes, and effective radii have been measured for 93 galaxies (i.e. the largest galaxies sample in the Washington system till now) from the FS90 Antlia Group catalogue. Membership of 37 objects can be confirmed through new radial velocities and data collected from the literature. The resulting colour–magnitude diagram shows that early‐type FS90 galaxies that are spectroscopically confirmed Antlia members or that were considered as definite members by FS90, follow a well‐defined CMR that spans 9 mag in brightness with no apparent change of slope. This relation is very tight for the whole magnitude range but S0 galaxies show a larger dispersion, apparently due to a separation of ellipticals and S0s. Antlia displays a slope of −13.6 in a T1 versus (C−T1) diagram, in agreement with results for clusters like Fornax, Virgo, Coma and Perseus, which are dynamically different to Antlia. This fact might indicate that the build‐up of the CMR in cluster of galaxies is more related to galaxies internal processes than to the influence of the environment. Interpreting the CMR as a luminosity–metallicity relation of old stellar systems, the metallicities of the Antlia galaxies define a global relation down to MV≈−13. We also find, for early‐type dwarfs, no clear relation between luminosity and effective radius, indicating a nearly constant mean effective radius of ∼1 kpc. This value is also found in several samples of dwarf galaxies in Virgo and Coma.

Relating basic properties of bright early-type dwarf galaxies to their location in Abell 901/902

“…The dotted line indicates an effective radius of r e = 1.41 kpc, which was found to be the typical size of dEs in the Virgo cluster (Boselli et al 2008b). Slightly smaller sizes were found for dE populations in the Antlia (Smith Castelli et al 2008) and Coma clusters, however with significantly smaller samples sizes. Figure 2a shows that among Es brighter galaxies have large effective radii.…”

“…The dEs in our sample are in good agreement with the Virgo fit, while the majority of Es are shifted towards redder colors. A nonlinear color−magnitude relation for a combined sample of giant and dwarf early-type galaxies has been reported by Janz & Lisker (2009), while linear color−magnitude relations have been found in recent photometric studies of nearby galaxy clusters (Misgeld et al 2008(Misgeld et al , 2009Smith Castelli et al 2008). We use this fit to further subdivide our dE sample, which is indicated in Fig.…”

Truncated star formation in dwarf spheroidal galaxies and photometric scaling relations

“…Bright elliptical galaxies, or Es, and dwarf elliptical galaxies, or dEs, follow the same photometric and kinematic scaling relations (Graham & Guzmán 2003, Matković & Guzmán 2005, Smith Castelli et al 2008. In the luminosity interval −24 mag M V −14 mag the parameters of the Sérsic profile follow simple power-laws as a function of luminosity and early and late type galaxies trace parallel Tully-Fisher relations (De Rijcke et al 2007).…”

“…Half of the D05 sample consists of dEs from the NGC5044 and NGC5989 groups. The data of the dSphs and dEs in the Antlia cluster are taken from Smith Castelli et al (2008). Data for the giant elliptical and for Coma dEs is taken from Graham & Guzmán (2003) (GG03).…”

Searching for star-forming dwarf galaxies in the Antlia cluster

“…This Antlia Cluster Project covers not only star-forming galaxies, but also globular clusters (Dirsch et al 2003;Bassino et al 2008), ultracompact dwarfs (UCDs: Caso et al 2013;Caso et al, in prep. ) and galaxy populations (Smith Castelli et al 2008a,b, 2012Calderón et al, in prep. ;Bassino et al, in prep.…”