Candidate Tidal Dwarf Galaxies in the Compact Group CG J1720-67.8

Abstract

This is the second part of a detailed study of the ultracompact group CG J1720-67.8: in the first part we have focused the attention on the three main galaxies of the group and we have identified a number of candidate tidal dwarf galaxies (TDGs). Here we concentrate on these candidate TDGs. Absolute photometry of these objects in BVRJHKs bands confirms their relatively blue colors, as we already expected from the inspection of optical and near-infrared color maps and from the presence of emission-lines in the optical spectra. The physical conditions in such candidate TDGs are investigated through the application of photoionization models, while the optical colors are compared with grids of spectrophotometric evolutionary synthesis models from the literature. Although from our data self-gravitation cannot be proved for these objects, their general properties are consistent with those of other TDG candidates. Additionally we present the photometry of a few ``knots'' detected in the immediate surroundings of CG J1720-67.8 and consider the possibility that these objects might belong to a dwarf population associated with the compact group.