The SAMI Galaxy Survey: bulge and disk stellar population properties in
  cluster galaxies
  We explore stellar population properties separately in the bulge and the disk
of double-component cluster galaxies to shed light on the formation of
lenticular galaxies in dense environments. We study eight low-redshift clusters
from the Sydney-AAO Multi-object Integral field (SAMI) Galaxy Survey, using 2D
photometric bulge-disk decomposition in the $g$, $r$ and $i$-bands to
characterize galaxies. For 192 double-component galaxies with
$M_{*}>10^{10~}M_{\odot}$ we estimate the color, age and metallicity of the
bulge and the disk. The analysis of the $g-i$ colors reveals that bulges are
redder than their surrounding disks with a median offset of 0.12$\pm$0.02 mag,
consistent with previous results. To measure mass-weighted age and metallicity
we investigate three methods: (i) one based on galaxy stellar mass weights for
the two components, (ii) one based on flux weights and (iii) one based on
radial separation. The three methods agree in finding 62% of galaxies having
bulges that are 2-3 times more metal-rich than the disks. Of the remaining
galaxies, 7% have bulges that are more metal-poor than the disks, while for 31%
the bulge and disk metallicities are not significantly different. We observe
23% of galaxies being characterized by bulges older and 34% by bulges younger
with respect to the disks. The remaining 43% of galaxies have bulges and disks
with statistically indistinguishable ages. Redder bulges tend to be more
metal-rich than the disks, suggesting that the redder color in bulges is due to
their enhanced metallicity relative to the disks instead of differences in
stellar population age.
