The Hα Luminosity Function and Star Formation Rate atz∼ 0.2

We have measured the Hα + [N II] fluxes of the I -selected Canada-France Redshift Survey (CFRS) galaxies lying at a redshift z below 0.3 and hence derived the Hα luminosity function. The magnitude limits of the CFRS mean that only the galaxies with M B ≳ -21 mag were observed at these redshifts. We obtained a total Hα luminosity density of at least 10 39.44±0.04 ergs s -1 Mpc -3 at a mean z = 0.2 for galaxies with rest-frame EW(Hα + [N II]) ≳ 10 Å. This is twice the value found in the local universe by Gallego et al. Our Hα star formation rate, derived from Madau, is higher than the UV observations at the same z , implying a UV dust extinction of ~1 mag. We found a strong correlation between the Hα luminosity and the absolute magnitude in the B band: M ( B AB ) = 46.7 - 1.6 log L (Hα). This work will serve as a basis of future studies of Hα luminosity distributions measured from optically selected spectroscopic surveys of the distant universe, and it will provide a better understanding of the physical processes responsible for the observed galaxy evolution.