The Calar Alto Deep Imaging Survey: $K$-band Galaxy number counts

We present K-band number counts for the faint galaxies in the Calar Alto Deep Imaging Survey (CADIS). We covered 4 CADIS fields, a total area of 0.2 deg^2, in the broad band filters B, R and K. We detect about 4000 galaxies in the K-band images, with a completeness limit of K = 19.75 mag, and derive the K-band galaxy number counts in the range of 14.25 18 mag. We also find that most of the K = 18 – 20 mag galaxies have a B - K color bluer than the prediction of a no-evolution model for an L⋆ Sbc galaxy, implying either significant evolution, even for massive galaxies, or the existence of an extra population of small galaxies.