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Issue A&A Volume 368, Number 3, March IV 2001 Page(s) 787 - 796 Section Extragalactic astronomy DOI 10.1051/0004-6361:20010057

A&A 368, 787-796 (2001)
DOI: 10.1051/0004-6361:20010057

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

J.-S. Huang^{1, 2}, D. Thompson^{3, 2}, M. W. Kümmel², K. Meisenheimer², C. Wolf², S. V. W. Beckwith^{4, 2}, R. Fockenbrock², J. W. Fried², H. Hippelein², B. von Kuhlmann², S. Phleps², H.-J. Röser² and E. Thommes<sup>2

1</sup>  Present address: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
²  Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
³  Present address: California Institute of Technology, MS 320-47, Pasadena, CA 91125, USA
⁴  Present address: STScI, 3700 San Martin Dr., Baltimore, MD 21218, USA

(Received 17 April 2000 / Accepted 4 January 2001)

Abstract
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 , in the broad band filters B, R and K. We detect about 4000 galaxies in the K-band images, with a completeness limit of , and derive the K-band galaxy number counts in the range of . This is the largest medium deep K-band survey to date in this magnitude range. The B- and R-band number counts are also derived, down to completeness limits of and . The K-selected galaxies in this magnitude range are of particular interest, since some medium deep near-infrared surveys have identified breaks of both the slope of the K-band number counts and the mean B-K color at . There is, however, a significant disagreement in the K-band number counts among the existing surveys. Our large near-infrared selected galaxy sample allows us to establish the presence of a clear break in the slope at from dlog N/dm = 0.64 at brighter magnitudes to dlog N/dm = 0.36 at the fainter end. We construct no-evolution and passive evolution models, and find that the passive evolution model can simultaneously fit the B-, R- and K-band number counts well. The B-K colors show a clear trend to bluer colors for . We also find that most of the K=18- 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.

Key words: cosmology: observations -- galaxies: evolution -- galaxy: formation -- surveys -- infrared: galaxies

Offprint request: J.-S. Huang, jhuang@cfa.harvard.edu

© ESO 2001

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