The Wyoming Survey for H-alpha. I. Initial Results at z ~ 0.16 and 0.24

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 ~1033 W 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 h 70 M ☉ 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.