The Photometric Redshift Distribution and Evolutionary Properties of Galaxies up to [CLC][ITAL]z[/ITAL][/CLC] ∼ 4.5 in the Field of the Quasar BR 1202−0725

We present a deep BVrIK multicolor catalog of galaxies in the field of the high redshift (z=4.7) quasar BR 1202-0725. Reliable colors have been measured for galaxies selected down to R=25. The choice of the optical filters has been optimized to define a robust multicolor selection of galaxies at 3.8 1.5. At variance with brighter surveys (I -19. The observed cosmological ultraviolet luminosity density is computed in the overall redshift interval z=0.3-4.5 reaching a value 2x10¹⁹ W/Hz/Mpc^3 at z~0.8. We have derived in a homogeneous way, using the GISSEL libraries, the physical parameters connected with the fitted spectral energy distributions. The bulk of the blue intermediate redshift population with z=0.4-1 mostly consists of very young star-forming galaxies with a median starburst age of the order of a few 10^8 yr and typical mass in luminous stars ~2x10^8 Mo.