Early-type galaxies: the last 10 billion years
 
I review our current understanding of the formation of early-type
galaxies (ETGs), in the context of studies that exploit rest-frame
UV-optical photometry. I show that, contrary to our classical notion
of them being old and passively evolving, ETGs host widespread star
formation at late epochs via persistent minor merging, which
contributes 20% of their stellar mass at the present day. Similarly,
while our traditional view has been that ETGs are remnants of gas-rich
major mergers at high redshift, I present empirical evidence that
argues against major mergers as the dominant mechanism for the
formation of these systems in the early Universe. Notwithstanding
their apparent homogeneity today, ETGs are a rather heterogeneous
population of galaxies, in which early mass growth was likely driven
either by direct accretion (‘cold flows’) or minor mergers at high
redshift.