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 226 < MK < 216 by a Schechter function with parameters a ˆ 21:16 ^ 0:19; M* ˆ 223:58 ^ 0:42 and f* ˆ 0:012 ^ 0:008 Mpc, assuming a Hubble constant of H0 ˆ 100 km s Mpc. We have also estimated the LF for two subsets of galaxies subdivided by the equivalent width of the Ha emission line at EW…Ha† ˆ 10 A. There is no significant difference in LF shape between the two samples, although there is a hint (,1s 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 a between the two samples.