Small Stellar Systems in Antlia: Globular Clusters and Dwarf Galaxies

BASSINO, L. ; SMITH CASTELLI, A. V.; RICHTLER, T.; CELLONE, S.; GÓMEZ, M.; INFANTE, L.; ARUTA, C.; DIRSCH, B.

Margarita

Congreso; XII Reunión Regional Latinoamericana de la IAU; 2007

International Astronomical Union (IAU)

The Antlia galaxy cluster is the third nearest galaxy cluster after Virgo and Fornax. While intermediate in richness between these two well investigated clusters, its galaxy density is even higher. In spite of its proximity, it has been hardly studied in the optical. Antlia exhibits a complex structure consisting of several subgroups, the  most important ones being dominated by the giant ellipticals  NGC3258 and NGC3268. We present the combined results of two  investigations:(1) A study of the globular cluster (GC) systems around NGC3258 and NGC3268 (Bassino et al., in prep.), on the basis of V; I photometry performed on FORS1-VLT images. The distance to the galaxies are determined by means of the GC luminosity functions. The GC colour distributions are bimodal, except for the brightest clusters which show unimodal distributions. The radial density profiles of the red (metal-rich) GCs follow closely the V brightness profiles of the galaxies. The azimuthal GC distributions and surface photometry of the galaxies, show that they are all elongated and aligned in a common direction, parallel to an axis joining the galaxies. This work presents several evidences that suggest the existence of tidal interaction processes, between both ellipticals.The existence of intracluster GCs is also discussed.(2) A study of Antlia dwarf galaxies in the central region of the cluster (Smith Castelli et al., in prep.), based on wide-field MOSAIC-CTIO images, obtained with Washington C and Kron-Cousins R filters. We analyze the colour-magnitude relation of early-type dwarf galaxies, previously listed in the Ferguson & Sandage´s (1990,  hereafter FS90) photographic Antlia Group Catalog. They show a very tight sequence on the colour-magnitude diagram (CMD). Besides, we find that diferent galaxies, placed in our central field, display an interesting segregation in the CMD, according to morphological type and membership status. Among the dwarf population of galaxies, we have found several new candidates not included in the FS90 catalog. In addition, we are studying the  properties of a couple of confirmed blue compact dwarf (BCD)  galaxies members of Antlia, as well as other BCD candidates located  in the field.