Gallego Maestro, JesúsZamorano Calvo, JaimeAragón Salamanca, A.Rego Fernández, Manuel2023-06-202023-06-201995-12-100004-637X10.1086/309804https://hdl.handle.net/20.500.14352/59816© 1995. The American Astronomical Society. We thank S. White, A. G. Vitores, O. Alonso, J. Gorgas, and N. Cardiel for their many valuable comments. This work was supported in part by the Spanish Programa Sectorial de Promoción del Conocimiento under grant PB93-456. A. A. S. acknowledges generous financial support from the Royal Society.The Universidad Complutense de Madrid (UCM) survey is a long-term project aimed at finding and analyzing star-forming galaxies detected by their Hα emission in Schmidt objective-prism plates. The instrumental setup limits the volume of the universe surveyed to a redshift z ≲ 0.045. So far we have discovered several hundred emission-line galaxies (ELGs) undergoing star formation at a wide range of levels. Analyzing a complete sample of ELGs from the UCM survey, we have computed the Hα luminosity function for the star-forming galaxies in the surveyed volume of the universe. A Schechter function provides a good fit to the H_α luminosity function with the following parameters: α = -1.3 ± 0.2, L^*(H_α) = 10^42.15±0.08 ergs s^-1, and φ^* = 10^-3.2±0.2 Mpc^3 for H_0 = 50 km s^-1 Mpc^-1. Integrating over the full range of luminosities, we obtain an H_α luminosity density of 10^39.1±0.2 ergs s^-1 Mpc^-3. Using the H_α emission as a star formation rate (SFR) estimator, this translates into a SFR density for the local universe of 0.013_−0.005^+0.007 M_☉ yr^-1 Mpc^-3 in star-forming galaxies with EW(H_α + [N_II]) > 10 Å and z lesssim 0.045 for a Scalo initial mass function. This is the first observational determination of this quantity, which will provide a direct test of current galaxy formation and evolution models.engjournal articlehttp://dx.doi.org/10.1086/309804http://iopscience.iop.org/open access52Emission-line galaxiesEvolutionAstrofísicaAstronomía (Física)