The K-band luminosity function of nearby field galaxies

We present a measurement of the K-band luminosity function (LF) of field galaxies obtained from near-infrared imaging of a sample of 345 galaxies selected from the Stromlo-APM Redshift Survey. The LF is reasonably well fitted over the 10-mag range −26⩽MK⩽−16 by a Schechter function with parameters α = −1.16±0.19, M* = −23.58±0.42 and φ* = 0.012±0.008 Mpc−3, assuming a Hubble constant of H0 = 100 km s−1 Mpc−1. We have also estimated the LF for two subsets of galaxies subdivided by the equivalent width of the Hα emission line at EW(Hα) = 10 Å. There is no significant difference in LF shape between the two samples, although there is a hint (∼1σ significance) that emission-line galaxies (ELGs) have M* roughly 1 mag fainter than non-ELGs. Contrary to the optical LF, there is no difference in faint-end slope α between the two samples.