The Current Star Formation Rate of the Local Universe

The Universidad Complutense de Madrid (UCM) survey is a long-term project aimed at finding and analyzing star-forming galaxies detected by their Ha 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 Ha luminosity function for the star-forming galaxies in the surveyed volume of the universe. A Schechter function provides a good fit to the Ha luminosity function with the following parameters: a 5 21.3 H 0.2, L*(Ha) 5 10 ergs s, and f* 5 10 Mpc for H0 5 50 km s Mpc. Integrating over the full range of luminosities, we obtain an Ha luminosity density of 10 ergs s Mpc. Using the Ha emission as a star formation rate (SFR) estimator, this translates into a SFR density for the local universe of 0.01320.005 10.007 MJ yr Mpc in star-forming galaxies with EW(Ha 1 [N II]) . 10 Å and z = 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. Subject headings: galaxies: fundamental parameters— galaxies: luminosity function, mass function