The formation and evolution of Virgo cluster galaxies - II. Stellar populations

We use a combination of deep optical and near-infrared light profiles for a morphologically diverse sample of Virgo cluster galaxies to study the radially resolved stellar populations of cluster galaxies over a wide range of galaxy structure. We find that, in the median, the age gradients of Virgo galaxies are either flat (lenticulars and Sa-Sb spirals) or positive (ellipticals, Sbc+Sc spirals, gas-rich dwarfs and irregulars), while all galaxy types have a negative median metallicity gradient. Comparison of the galaxy stellar population diagnostics (age, metallicity and gradients thereof) against structural and environmental parameters also reveals that the ages of gas-rich systems depend mainly on their atomic gas deficiencies. Conversely, the metallicities of Virgo gas-poor galaxies depend on their concentration, luminosity and surface brightness. The stellar population gradients of all Virgo galaxies exhibit no dependence on either their structure or environment. The stellar populations of gas-poor giants (E/S0s) are consistent with a hierarchical formation, wherein the stars in more massive systems were largely formed out of dissipative starbursts associated with gas-rich merging. Differences in the stellar population properties of gas-poor dwarfs and giants suggest different origins for them. The stellar populations in Virgo dS0s and dEs also lack uniformity, suggesting that the formation of Virgo gas-poor dwarfs proceeded through at least two different channels (environmental transformation and merging). Finally, the present stellar content of Virgo spirals seems to have been largely regulated by environmental effects. Spirals with positive age gradients (largely gas-poor types) are likely evolutionary remnants of progenitors which were stripped of their gas discs due to prolonged exposure to the intercluster medium wind. Spirals with negative age gradients are consistent with a traditional inside-out disc growth scenario and have likely not been affected by their environment yet. The paucity of flat stellar population gradients in Virgo spirals suggests that secular evolution is likely not responsible for the formation of their bulges.