AN IMAGING K-BAND SURVEY - II: THE REDSHIFT SURVEY AND GALAXY EVOLUTION IN THE INFRARED

We present a redshift survey of 124 galaxies, from an imaging $K$-band survey complete to $K\simeq 17.3$. The optical-to-infrared colours are consistent with the range expected from synthetic galaxy spectra, although there are some cases of very red nuclei. Our data show no evidence for evolution of the $K$-band luminosity function at $z<0.5$, and the results are well described by a Schechter function with $M_K^{\ast }=-22.75\pm 0.13+5{\log }_{10}h$ and ${\varphi }^{\ast }=0.026\pm 0.003h^3\mathrm{M}\mathrm{p}{\mathrm{c}}^{-3}$. This is a somewhat higher normalization than has been found by previous workers, and it removes much of the excess in faint $K$ and $B$ counts with respect to a no-evolution model. However, we do find evidence for evolution at $z>0.5$: $M_K^{\ast }$ is approximately 0.75 mag. brighter at $z=1$. This luminosity evolution is balanced by a reduced normalization at high redshift. The overall evolution is thus opposite to that expected in simple merger-dominated models.