2008AJ....135.1412D

The Wyoming Survey for Hα, or WySH, is a large-area, ground-based, narrowband imaging survey for Hα-emitting galaxies over the latter half of the age of the universe. The survey spans several square degrees in a set of fields of low Galactic cirrus emission. The observing program focuses on multiple Δz ∼ 0.02 epochs from z ∼ 0.16 to z ∼ 0.81 down to a uniform (continuum+line) luminosity at each epoch of ∼10³³W uncorrected for extinction (3σ for a 3' diameter aperture). First results are presented here for 98+208 galaxies observed over approximately 2 deg² at redshifts z ∼ 0.16 and 0.24, including preliminary luminosity functions at these two epochs. These data clearly show an evolution with lookback time in the volume-averaged cosmic star-formation rate. Integrals of Schechter fits to the extinction-corrected Hα luminosity functions indicate star-formation rates per co-moving volume of 0.009 and 0.014 h₇₀M_☉.yr^–1.Mpc^–3 at z ∼ 0.16 and 0.24, respectively. The formal uncertainties in the Schechter fits, based on this initial subset of the survey, correspond to uncertainties in the cosmic star formation rate density at the ≳40% level; the tentative uncertainty due to cosmic variance is 25%, estimated from separately carrying out the analysis on data from the first two fields with substantial datasets.