The Near‐Infrared Number Counts and Luminosity Functions of Local Galaxies

This study presents a wide-field near-infrared (K-band) survey in two fields;SA 68 and Lynx 2. The survey covers an area of 0.6 deg.$^2$, complete toK=16.5. A total of 867 galaxies are detected in this survey of which 175 haveavailable redshifts. The near-infrared number counts to K=16.5 mag. areestimated from the complete photometric survey and are found to be in closeagreement with other available studies. The sample is corrected forincompleteness in redshift space, using selection function in the form of aFermi-Dirac distribution. This is then used to estimate the local near-infraredluminosity function of galaxies. A Schechter fit to the infrared data gives:M$^\ast_K = -25.1 \pm 0.3$, $\alpha = -1.3\pm 0.2$ and $\phi^\ast =(1.5\pm0.5)\times 10^{-3}$ Mpc$^{-3}$ (for H$_0=50$ Km/sec/Mpc and q$_0=0.5$). Whenreduced to $\alpha=-1$, this agrees with other available estimates of the localIRLF. We find a steeper slope for the faint-end of the infrared luminosityfunction when compared to previous studies. This is interpreted as due to thepresence of a population of faint but evolved (metal rich) galaxies in thelocal Universe. However, it is not from the same population as the faint bluegalaxies found in the optical surveys. The characteristic magnitude($M^\ast_K$) of the local IRLF indicates that the bright red galaxies ($M_K\sim-27$ mag.) have a space density of $\le 5\times 10^{-5}$ Mpc$^{-3}$ and hence,are not likely to be local objects.Comment: 24 pages, 8 figures, AASTEX 4.0, published in ApJ 492, 45