Colors of Luminous Bulges in Cluster MS 1054-03 and Field Galaxies at Redshifts z ~ 0.83

Using HST images, we separate the bulge-like (pbulge) and disk-like (pdisk)components of 71 galaxies in the rich cluster MS1054-03 and of 21 in the field.Our key finding is that luminous pbulges are very red with restframe U-B ~0.45, while predicted colors are bluer by 0.20 mag. Moreover, these very redcolors appear to be independent of environment, pbulge luminosity, pdisk color,and pbulge fraction. These results challenge any models of hierarchical galaxyformation that predict the colors of distant (z ~ 0.8) luminous field andcluster bulges would differ. Our findings also disagree with other claims that30% to 50% of bright bulges and ellipticals at z ~ 1 are very blue (U-B < 0).Comment: 5 pages and 1 figure. Accepted for publication in ApJ Letter