Where is the Light? Tracing the Evolution of Bulges and Disks since z ~ 0.8†

Abstract The chronology of galactic bulge and disk formation is studied by analysing the relative contributions of these components to the B band rest–frame luminosity density (LD) at two different cosmological epochs. The luminosity function (LF) of the bulge and disk components at z ~ 0.8 is computed on a galaxy subsample of the final zCOSMOS “bright” catalogue of roughly 20,000 objects with spectroscopic redshift in the COSMOS field. The comparison is then performed on galaxies in the local universe. Our preliminary results show that the LD in the disk component strongly decreases from ~ 80% at z ~ 0.8 to ~ 50% at z = 0, the bulges having a specular behaviour. The observational constraints provided in this work are aimed to discriminate among competing scenarios of galaxy formation and evolution. An appropriate comparison with hydrodynamical semianalytical models will be considered in a future study to understand further the formation and evolution of galaxies.

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