Photometric and morphological analysis of UCM galaxies .2. Statistical results and interpretation

Abstract

We present the results of Thuan & Gunn r CCD imaging observations of the Universidad Complutense de Madrid (UCM) sample of emission-line galaxies (ELGs) selected by the presence of H_α emission in low resolution objective-prism spectra. In this work, a total of 212 objects from the UCM survey have been photometrically and morphologically characterized. In a previous paper, the observations, basic reductions and morphological classification for the UCM objects were presented. Here, we analyse the statistical properties of the sample and their interpretations. The main results obtained are as follows: (1) Our survey is specially effective in the detection of ELGs smaller and less luminous than normal spirals (the median values of the UCM sample are M_r = -20.6 and D_24 = 19.4 kpc, for H_0 = 50 km s^-1 Mpc^-1). (2) The sample presents a very heterogeneous morphological population of galaxies. There is a clear predominance of late-type galaxies, with 66% being Sb or later. (3) We have found a set of galaxies specially interesting. In particular, we propose 9 candidates to BCD (blue compact dwarf galaxy), five of them previously unknown. (4) About 10% of the ELGs of the sample show typical parameters of S0 types, and in the subsample of 16 UCM interacting galaxies, 25% are S0 type galaxies. (5) In the set of UCM galaxies inside the Coma cluster, 71% exhibit Hubble types Sb or later.