Early-type galaxies across the UV-optical color magnitude diagram

With the aim to clarify the mechanisms driving the evolution of galaxies in nearby groups, we focus on Early-Type galaxies (ETGs) of two groups in the Leo cloud. Using SPH simulations with chemo-photometric implementation, we match kinematical, photometric and morphological properties of ETGs to trace back their evolution. We follow ETG evolution in the rest-frame UV-optical color magnitude diagram (CMD), from the blue cloud (BC) to the red sequence (RS), through the green valley (GV). ETGs brighter than Mr ~ -21 mag are old (13-14 Gyr) and spend up to 10 Gyr in the BC before they reach the RS. ETGs fainter than Mr=-21 mag are slightly younger (11-12 Gyr), and spend about 7-8 Gyrs in the BC. All ETGs cross the GV in about 3-4 Gyr, the turn-off occurs at z~ 0.3-0.4. For UGC 6324, the faintest ETG in our sample, simulations predict strong oscillations in the GV. We conclude that ETGs evolution in the two groups is driven by gravitational mechanisms such as merging and/or interactions which may happen before or during the collapse phase of groups.