The Hα Luminosity Function and Star Formation Rate atz∼ 0.2

We have measured the Ha+[N II] fluxes of the I-selected Canada-FranceRedshift Survey (CFRS) galaxies lying at a redshift z below 0.3, and hencederived the Ha luminosity function. The magnitude limits of the CFRS mean thatonly the galaxies with M(B) > -21 mag were observed at these redshifts. Weobtained a total Ha luminosity density of at least 10^{39.44\pm 0.04}erg/s/Mpc^{3} at a mean z=0.2 for galaxies with rest-fame EW(Ha+[N II]) > 10Angs. This is twice the value found in the local universe by Gallego et al.1995. Our Ha star formation rate, derived from Madau (1997) is higher than theUV observations at same z, implying a UV dust extinction of about 1 mag. Wefound a strong correlation between the Ha luminosity and the absolute magnitudein the B-band: M(B(AB)) = 46.7 - 1.6 log L(Ha). This work will serve as a basisof future studies of Ha luminosity distributions measured fromoptically-selected spectroscopic surveys of the distant universe, and it willprovide a better understanding of the physical processes responsible for theobserved galaxy evolution.Comment: Accepted for publication in ApJ, 14 pages, LaTeX (macro aas2pp4.sty), 6 figure