The Wyoming Survey for Hα. II. Hα Luminosity Functions at z 0.16, 0.24, 0.32, and 0.40

The Wyoming Survey for Hα, or WySH, is a large-area, ground-based imaging survey for Hα-emitting galaxies at redshifts of z 0.16, 0.24, 0.32, and 0.40. The survey spans up to 4 deg2 in a set of fields of low Galactic cirrus emission, using twin narrowband filters at each epoch for improved stellar continuum subtraction. Hα luminosity functions are presented for each Δz 0.02 epoch based on a total of nearly 1200 galaxies. These data clearly show an evolution with look-back time in the volume-averaged cosmic star formation rate. Integrals of Schechter fits to the incompleteness- and extinction-corrected Hα luminosity functions indicate star formation rates per comoving volume of 0.010, 0.013, 0.020, 0.022 h 70 M ☉ yr–1 Mpc–3 at z ~ 0.16, 0.24, 0.32, and 0.40, respectively. Combined statistical and systematic measurement uncertainties are on the order of 25%, while the effects of cosmic variance are at the 20% level. The bulk of this evolution is driven by changes in the characteristic luminosity L * of the Hα luminosity functions, with L * for the earlier two epochs being a factor of 2 larger than L * at the latter two epochs; it is more difficult with this data set to decipher systematic evolutionary differences in the luminosity function amplitude and faint-end slope. Coupling these results with a comprehensive compilation of results from the literature on emission line surveys, the evolution in the cosmic star formation rate density over 0 z 1.5 is measured to be .