We investigate the growth of bulges in bright (MB < −20) disc galaxies since z ∼ 1, in restframe B and I-band, using images from HST ACS and WFC3 in GOODS-South for high redshifts (0.4 < z < 1.0) and SDSS for local (0.02 < z < 0.05). The growth history x been traced by performing two-component bulge-disc decomposition and further classifying the bulges into pseudos and classicals using 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 z ∼ 0.77, classical 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 z ∼ 1. Their host discs have grown concurrently, becoming progressively brighter in rest-frame I-band. The high redshift host discs 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 discs - which might be an indication of secular processes in action. However, both host disc as well as the bulge have grown substantially in terms of stellar mass. Our analysis suggests that, clump migration and secular processes alone can not account for the bulge growth, since z ∼ 1, accretion and minor mergers would be required.
Sonali Sachdeva and Kanak Saha
arXiv,( accepted for publication in ApJ)回上一頁