Fundamental relations of early-type galaxies in the Antlia cluster

CALDERÓN, J. P.; BASSINO, L. P.; CELLONE, S. A.; CASO, J. P.; RICHTLER, T.; GOMEZ, M.

Santiago

Workshop; Deconstructing Galaxies: Structure and Morphology in the Era of Large Surveys (ESO Workshop); 2013

ESO

The Antlia Cluster is the third nearest populous galaxy cluster, after Fornax and Virgo, at a distance of ~35 Mpc. The first study previous to our present project was the photographic catalogue by Ferguson & Sandage (1990, FS90), which identified 375 galaxies. Due to its proximity and large population, the Antlia cluster is a quite interesting target to study the galaxies´ structure and morphology, with the final aim to contribute to a better understanding of the origin and evolution of galaxies. The observational material used for this study consists of CCD images of four MOSAIC fields (36" x 36") obtained at the Blanco 4-m telescope at CTIO, in R (Kron-Cousins) and C (Washington) filters, and GEMINI/GMOS spectra to confirm membership. Surface photometry was performed for about 240 early-type Antlia galaxies, by means of IRAF tasks plus our own scripts. We fitted Sérsic models to their surface brightness profiles and characterized the galaxy sample according to total magnitudes and colours, effective radius, effective surface brightness, and Sérsic index N. In all cases, we fitted one or two components, depending on the residuals systematic behavior. Out of the total sample, 60% of the galaxies had been catalogued by FS90, while the rest are newly discovered galaxies. Finally, we built the fundamental relations that involve the photometric and structural parameters for the early-type galaxies, i.e. colour vs. magnitude, effective surface brightness vs. effective radius, effective surface brightness vs. magnitude, the respective relations with the N index, etc. Taking into account that bright galaxies in Antlia are mostly lenticulars and few ellipticals, these fundamental relations show that the dwarf galaxies in this cluster follow different sequences than their brighter counterparts.