Growth of Bulges in Disk Galaxies Since z ∼ 1

Abstract

Abstract We investigate the growth of bulges in bright ( ) disk galaxies since , in rest-frame B and I-band, using images from HST ACS and WFC3 in GOODS-South for high redshifts ( ) and SDSS for local ( ). The growth history has been traced by performing two-component bulge-disk decomposition and further classifying the bulges into pseudos and classicals using the Kormendy relation. We have about 27% pseudo and 40% classical bulges in our sample. Classical bulges are brighter than pseudo, in both rest-bands, at all redshifts probed here; in fact since , classicals are about ∼1 mag brighter than pseudo bulges. Both bulges have witnessed substantial growth, more than half of their present-day stellar mass has been gained since . Their host disks have grown concurrently, becoming progressively brighter in rest-frame I-band. The high-redshift host disks of both pseudo and classical bulges are found to be equally clumpy in rest-frame B-band. In the same band, we found that the growth of classical bulges is accompanied by fading of their host disks—which might be an indication of secular processes in action. However, both host disk as well as the bulge have grown substantially in terms of stellar mass. Our analysis suggests that clump migration and secular processes alone cannot account for the bulge growth, since , accretion, and minor mergers would be required.