The Origin of S0s in Clusters: evidence from the bulge and disc star
  formation histories
  The individual star formation histories of bulges and discs of lenticular
(S0) galaxies can provide information on the processes involved in the
quenching of their star formation and subsequent transformation from spirals.
In order to study this transformation in dense environments, we have decomposed
long-slit spectroscopic observations of a sample of 21 S0s from the Virgo
Cluster to produce one-dimensional spectra representing purely the bulge and
disc light for each galaxy. Analysis of the Lick indices within these spectra
reveals that the bulges contain consistently younger and more metal-rich
stellar populations than their surrounding discs, implying that the final
episode of star formation within S0s occurs in their central regions. Analysis
of the $\alpha$-element abundances in these components further presents a
picture in which the final episode of star formation in the bulge is fueled
using gas that has previously been chemically enriched in the disc, indicating
the sequence of events in the transformation of these galaxies. Systems in
which star formation in the disk was spread over a longer period contain bulges
in which the final episode of star formation occurred more recently, as one
might expect for an approximately coeval population in which the transformation
from spiral to S0 occurred at different times. With data of this quality and
the new analysis method deployed here, we can begin to describe this process in
a quantitative manner for the first time.
