A faint galaxy redshift survey to B=24

Abstract

Using the multislit LDSS-2 spectrograph on the William Herschel Telescope, we have completed a redshift survey in the magnitude range 22.5<B<24 which has produced 73 redshifts, representing a 73 per cent complete sample uniformly selected from four deep fields at high Galactic latitude. The survey extends out to z>1 and includes the highest redshift galaxy (z=1.108) yet discovered in a field sample. The median redshift, z_MED=0.46, and form of the redshift distribution constitute compelling evidence against simple luminosity evolution as an explanation of the large excess of faint galaxies [~=(2-4)xno-evolution] seen in this magnitude range. Rather, we identify the excess population as blue objects with z~0.4 and B luminosities similar to local L^* galaxies, indicating a dramatic decrease in the density of such objects over the last Hubble time, and confirming the trends found in brighter redshift surveys. We also find a marked absence of very low-redshift galaxies (z<0.1) at faint limits, severely constraining any significant steepening of the local field galaxy luminosity function at low luminosities.