A European Southern Observatory Very Large Telescope Survey of Near-Infrared (Z ≤ 25) Selected Galaxies at Redshifts 4.5 < z < 6: Constraining the Cosmic Star Formation Rate near the Reionization Epoch

We present the results of a Very Large Telescope (VLT) and Hubble Space Telescope imaging survey aimed at the identification of 4.5 4.5 galaxies. The resulting integral surface density of the ZAB 4.5 is in the range 0.13-0.44 arcmin-2, and that in the highest redshift bin 5 < z ? 6 is between 0.07 and 0.13 arcmin-2. In the two HDFs, we identify 25 galaxies at IAB ? 27.2 in the range 4.5 ? z < 5 and 16 at 5 ? z ? 6, corresponding to surface densities of 3.1 and 2 arcmin-2, respectively. We show that the observed ZAB < 25 UV luminosity density (LD) appears to drop by about 1 order of magnitude from z 3 to 6. However, if we apply a threshold to obtain an absolute magnitude-limited sample, the UV LD is roughly constant up to z 6. We finally show that recent semianalytic hierarchical models for galaxy formation, while predicting a nearly constant total UV LD up to z 6, underpredict the observed UV LD at ZAB ? 25 and overpredict the IAB ? 27.2 one. This behavior can be understood in terms of a poor match to the slope of the UV luminosity function.