Recent star formation in high-redshift early-type galaxies: insights from the rest-frame UV

摘要

We combine deep UBVRIzJK photometry from the MUSYC survey with redshiftsfrom the COMBO-17 survey to study the rest-frame ultraviolet (UV) properties of 674 high-redshift early-type galaxies, drawn from the Extended Chandra Deep Field South(E-CDFS). Galaxy morphologies are determined through visual inspection of Hubble SpaceTelescope (HST) images taken from the GEMS survey. We harness the sensitivity of the UVto young (1 Gyrs old) stars to quantify the recent star formation history of the early-typepopulation. We find compelling evidence that early-types of all luminosities form stars over thelifetime of the Universe, although the bulk of their star formation is already complete at highredshift. Luminous early-types form 10-15 percent of their mass afterz, while their less luminous counterparts form 30-60 percent of their massin the same redshift range.