Investigating early-type galaxy evolution with a multi-wavelength
  approach. III. Insights from SPH simulations with chemo-photometric
  implementation
  We are exploring galaxy evolution in low density environments exploiting
smooth particle hydrodynamic simulations including chemo-photometric
implementation. From a large grid of simulations of galaxy encounters and
mergers starting from triaxial halos of gas e dark matter, we single out the
simulations matching the global properties of our targets. These simulations
are used to give insights into their evolution. We focus on 11 early-type
galaxies selected because of their nearly passive stage of evolution in the
nuclear region. However, a variety of UV features are detected in more than
half of these galaxies. We find no significant differences in the formation
mechanisms between galaxies with or without UV features. Major and minor
mergers are able to reproduce their peculiar UV morphologies, galaxy encounters
are more suitable for 'normal' early-type galaxies. Their star formation rate
self-quenches several Gyr later the merger/encounter occurred, via gas
exhaustion and stellar feedback, moving the galaxy from blue to red colors,
driving the galaxy transformation. The length of the quenching is mass
dependent and lasts from 1 to 5 Gyr or more in the less massive systems. All
our targets are gas rich at redshift 1. Three of them assembled at most 40% of
their current stellar mass at z>1, and seven assembled more than 50% between
redshift 0.5 and 1. Their stellar mass grows with 4% by crossing the Green
Valley before reaching their current position on the NUV-r vs. Mr diagram.
