2010ApJ...712L.189D

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 h₇₀M_☉/yr/Mpc3 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 {dot}ρ_SFR(z) = {dot}ρ_SFR(0) (1+z)^3.4±0.4.