Spectroscopic properties and luminosity distribution of the Universidad Complutense de Madrid survey galaxies

A spectroscopic analysis of the entire sample of Ha emission-line galaxies (ELGs) contained in lists 1 and 2 of the Universidad Complutense de Madrid (UCM) objective-prism survey is presented. A significant fraction (59%) of star-forming galaxies with low-ionization or high-extinction properties has been found. This kind of ELG is only incompletely detected in the blue or in other ELG surveys. We have found evidence for evolution among some of the different ELG classes. A comparison between the populations detected by the Case, Kiso, University of Michigan, and UCM surveys is presented. We conclude that a deep H alpha survey is better able to sample all the ages, evolutionary stages, and luminosities of currently star-forming galaxies than other surveys using blue emission lines or colors. Finally, the luminosity and spatial distributions of the UCM galaxies are determined. The contribution of the newly found, currently star-forming ELGs provides new clues to galaxy evolution and has to be taken into account when trying to consider the density of ELGs and total star formation rate in the universe.