The similar stellar populations of quiescent spiral and elliptical
  galaxies
  We compare the stellar population properties in the central regions of
visually classified non-starforming spiral and elliptical galaxies from Galaxy
Zoo and SDSS DR7. The galaxies lie in the redshift range $0.04<z<0.1$ and have
stellar masses larger than $logM_*=10.4$. We select only face-on spiral
galaxies in order to avoid contamination by light from the disk in the SDSS
fiber and enabling the robust visual identification of spiral structure.
Overall, we find that galaxies with larger central stellar velocity
dispersions, regardless of morphological type, have older ages, higher
metallicities, and an increased overabundance of alpha-elements. Age and
alpha-enhancement, at fixed velocity dispersion, do not depend on morphological
type. The only parameter that, at a given velocity dispersion, correlates with
morphological type is metallicity, where the metallicity of the bulges of
spiral galaxies is 0.07 dex higher than that of the ellipticals. However, for
galaxies with a given total stellar mass, this dependence on morphology
disappears. Under the assumption that, for our sample, the velocity dispersion
traces the mass of the bulge alone, as opposed to the total mass (bulge+disk)
of the galaxy, our results imply that the formation epoch of galaxy and the
duration of its star-forming period are linked to the mass of the bulge. The
extent to which metals are retained within the galaxy, and not removed as a
result of outflows, is determined by the total mass of the galaxy.
