ENVIRONMENTAL PROPERTIES OF VIOLENTLY STAR-FORMING GALAXIES

A sample of 71 objects from the Spectrophotometric Catalogue of H II galaxies (Terlevich et al. 1990) has been searched for neighbouring objects. According to the metallicity, IRAS colours, morphology and environmental circumstances the objects have been classified in 6 different groups. Specific denominations are proposed for each class, from nuclear starburst galaxies to irregular blue galaxies and blue compact dwarf galaxies. Blue irregular and blue compact objects have lower metallicities and higher f25-mu-m/f 100-mu-m colour indices than nuclear starburst objects, indicating different evolutionary histories. All the nuclear starbursts and blue irregulars have massive companions, but only 2/3 of the blue compacts do have. The hypothesis of cloud-cloud collisions or galaxy-galaxy interactions to understand the triggering mechanism for the violent star formation are briefly discussed. It is stressed that the overall properties for isolated and non-isolated blue compact dwarf galaxies are similar irrespective of the possible triggering mechanism to induce the observed burst of star formation.