THE PROGENITORS OF LOCAL ULTRA-MASSIVE GALAXIES ACROSS COSMIC TIME: FROM DUSTY STAR-BURSTING TO QUIESCENT STELLAR POPULATIONS

Using the Ultra VISTA catalogs, we investigate the evolution in the 11.4 Gyr since z = 3 of the progenitors of local ultra-massive galaxies (log(M sub(star)/M sub([middot in circle])) approximately 11.8; UMGs), providing a complete and consistent picture of how the most massive galaxies at z = 0 have assembled. Our findings indicate that at least half of the stellar content of local UMGs was assembled at z > 1, whereas the remaining was assembled via merging from z ~ 1 to the present. Most of the quenching of the star-forming progenitors happened between z = 2.75 and z = 1.25, in good agreement with the typical formation redshift and scatter in age of z = 0 UMGs as derived from their fossil records. We propose an alternative path for the formation of local UMGs that refines previously proposed pictures and that is fully consistent with our findings.