The ESO K'-band Galaxy Survey - Galaxy Counts

We present K’-band galaxy counts in the magnitude range $13<K^{\mathrm{\prime }}<20$, obtained from two independent surveys near the South Galactic Pole, covering an area of $\sim 40arcmi{n}^2$ and $\sim 170arcmi{n}^2$, including $\sim 200$ and $\sim 1000$ objects respectively up to a magnitude limit $K^{\mathrm{\prime }}\sim 20.0$ and $K^{\mathrm{\prime }}\sim 19.0$. At magnitudes $K>18.5$ we surveyed an area more than 7 times wider that covered by previous K-band surveys. Our counts are quite in good agreement with those in the literature at magnitudes brighter than $K\sim 17$, while are systematically lower at fainter magnitudes. We confirm a change in the slope of the $dlogN\mathrm{/}dm$ relation at $K^{\mathrm{\prime }}\sim 17$ from 0.57 to 0.35, but do not find the bump shown by other K-band surveys in the magnitude range $16 < K < 20$\mathrm{.}Furthermore10$K’ \sim 18$have$B-K’<3$. We suggest that these blue objects represent a population of sub-$L^{\ast }$ nearby evolving galaxies.