Abstract:
I shall present recent results on stellar population gradients at large galactocentric radii for a sample of early-type galaxies covering a broad mass range, i.e. from Fornax and Virgo cluster dwarf ellipticals to brightest cluster/group galaxies. Focusing on the newly discovered correlation (Spolaor et al. 2009; Spolaor et al. 2010b) between metallicity gradients and galaxy mass, I shall examine how the interplay between dissipational processes and feedback mechanisms has driven the chemical evolutionary history of these early-type galaxies. The analysis of spatially resolved stellar population radial profiles of age, metallicity and alpha-elements abundance ratio at galactocentric radii as large as 3 times the galaxy effective radius, allows us to investigate the history of almost 60% of a galaxy total stellar mass and to examine the effects of local and global mechanisms of galaxy formation. The results are interpreted in comparison with competing chemodynamical model predictions. We find that an early star forming collapse could have acted as the main mechanisms for the formation of low-mass galaxies, with star formation efficiency increasing with galactic mass. More massive galaxies, above the mass threshold of 3.5 x 10^10 M_sun, might have formed by mergers of gas-rich disk galaxies and then subsequently evolved growing their mass via dry merger events. The varying efficiency of the dissipative merger-induced starburst and feedback processes have shaped the radial metallicity gradients in these high-mass systems.