The ESO K'-band galaxy survey .1. Galaxy counts

We present K'-band galaxy counts in the magnitude range 13<K'<20, obtained from two independent surveys near the South Galactic Pole, covering an area of similar to 40 arcmin(2) and similar to 170 arcmin(2), including similar to 200 and similar to 1000 objects up to a magnitude limit K'similar to 20 and K'similar to 19, respectively. At magnitudes K>18.5 we surveyed an area more than 7 times the one covered by previous K-band surveys. Our counts are in quite good agreement with those in the literature at magnitudes brighter than K similar to 17, while being systematically lower at fainter magnitudes. We confirm a change in the slope of the d log N/dm relation at K'similar to 17 from 0.57 to 0.35, but do not find the bump shown by other K-band surveys in the magnitude range 16<K<20. Furthermore 10% of the galaxies brighter than K'similar to 18 have B-K'<3. We suggest that these blue objects represent a population of sub-L* nearby evolving galaxies. (C) 1997 American Astronomical Society.