Bright Compact Bulges (BCBs) at intermediate redshifts
  Studying bright ($M_B<-20$), intermediate-redshift ($0.4<z<1.0$), disc
dominated ($n_B<2.5$) galaxies from HST/ACS and WFC3 in Chandra Deep Field
South, in rest-frame B and I-band, we found a new class of bulges which is
brighter and more compact than ellipticals. We refer to them as "Bright,
Compact Bulges" (BCBs) - they resemble neither classical nor pseudo-bulges and
constitute $\sim12$% of the total bulge population at these redshifts.
Examining free-bulge $+$ disc decomposition sample and elliptical galaxy sample
from Simard et al. (2011), we find that only $\sim0.2$% of the bulges can be
classified as BCBs in the local Universe. Bulge to total ratio $(B/T)$ of disc
galaxies with BCBs is (at $\sim0.4$) a factor of $\sim2$ and $\sim4$ larger
than for those with classical and pseudo bulges. BCBs are $\sim2.5$ and $\sim6$
times more massive than classical and pseudo bulges. Although disc galaxies
with BCBs host the most massive and dominant bulge type, their specific star
formation rate is $1.5-2$ times higher than other disc galaxies. This is
contrary to the expectations that a massive compact bulge would lead to lower
star formation rates. We speculate that our BCB host disc galaxies are
descendant of massive, compact and passive elliptical galaxies observed at
higher redshifts. Those high redshift ellipticals lack local counterparts and
possibly evolved by acquiring a compact disc around them. The overall
properties of BCBs supports a picture of galaxy assembly in which younger discs
are being accreted around massive pre-existing spheroids.
