Stellar Populations and Radial Migrations in Virgo Disk Galaxies

We present stellar age profiles for 64 Virgo cluster disk galaxies whose analysis poses a challenge for current galaxy formation models. Our results can be summarized as follows: first, and contrary to observations of field galaxies, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically-significant inversions ("U-shapes") in the age profiles of all three disk galaxy types, reminescent of predictions from high-resolution simulations of classically-truncated Type II disks in the field. These features characterize the age profiles for only about a third (<36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks (~11% of the total sample), exhibit age profiles which decrease outwards (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail (>50%) within our Type I, II and III sub-samples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their bretheren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment. Current disk galaxy formation models fail to reproduce these results, thus calling for adequate hydrodynamical simulations of dense galaxy environments, for which the current paper provides many constraints. [Abridged]