The star formation rate at redshift one:: Hα spectroscopy with CIRPASS

We have conducted an H alpha survey of 38 0.77 <= z <= 1 galaxies over similar to 100 arcmin(2) of the Hubble Deep Field-North and Flanking Fields, to determine star formation rates (SFRs), with the near-IR multi-object spectrograph Cambridge Infrared Panoramic Survey Spectrograph (CIRPASS) on the William Herschel Telescope (WHT). This represents the first successful application of this technique to observing high-redshift galaxies. Stacking the spectra in the rest frame to infer a total SFR for the field, we find a lower limit (uncorrected for dust reddening) on the SFR density at redshift z = 1 of 0.04M(circle dot) yr(-1) Mpc(-3). This implies rapid evolution in the SFR density from z = 0 to 1 which is proportional to (1 + z)(3.1).