The K20 survey - IV. The redshift distribution of $K_{\rm s}<20$ galaxies: A test of galaxy formation models

We present the redshift distribution of a complete sample of 480 galaxies with $K_{\rm s} 2 . The redshift completeness is 87% and 98% respectively with spectroscopic and high-quality and tested photometric redshifts. The redshift distribution of field galaxies has a median redshift $z_{\rm med}\sim 0.80$, with ~32% and ~9% of galaxies at $z>1$ and $z>1.5$ respectively. A “blind” comparison is made with the predictions of a set of the most recent Λ CDM hierarchical merging and pure luminosity evolution (PLE) models. The hierarchical merging models overpredict and underpredict the number of galaxies at low- z and high- z respectively, whereas the PLE models match the median redshift and the low- z distribution, still being able to follow the high- z tail of $N(z)$. We briefly discuss the implications of this comparison and the possible origins of the observed discrepancies. We make the redshift distribution publicly available.