Abstract

We explore the possibility of using a semi-analytic model of galaxy formation and evolution (SAG2, [1]) to assign intrinsic physical properties to a sample of real galaxies with known photometry. As the photometric sample, we use the extended chandra deep field south (E-CDFS) as sampled by the MUSYC survey (MUltiwavelength Survey by Yale-Chile, [2]), a photometric 2D survey that uses the UBVRIz optical filters, plus the NIR JK filters. The idea is to generate a catalog of semi-analytic galaxies whose intrinsic properties (i.e. absolute rest-frame magnitudes, stellar mass and redshift of the galaxies) are already known. Then, absolute magnitudes, stellar mass and redshift of each galaxy in the MUSYC sample are obtained by calculating the mean of this properties for those semi-analytic galaxies whose model-predicted apparent magnitudes fall within 1-sigma of the uncertainties of the MUSYC galaxies photometry. Finally, the redshifts assigned with this method to the photometric galaxy sample are used as a test for the method, comparing them with the spectroscopically determined redshifts of a subsample of galaxies. We conclude that this method gives a photometric redshift determination that has a mean normalized difference ([Zphot]/(1+phot)> with respect to the spectroscopic redshifts of 0.12 in the range of phot 2, with an optimal range of 0.3 phot1-4, where the mean normalized difference is ~ 0.06, which is in par with currently used photometric redshift determination methods [3].