Early-type galaxy formation history from GALEX-SAURON

One of long-standing debates in modern astrophysics is the formation mechanism of early-type galaxies. The classical model, proposed by Eggel et al. (1962), explains that early-type stellar populations form in an initial highly efficient burst and evolve without further star formation until present day. The high Mg and alpha abundances found in bright elliptical galaxies support such scenarios. Early-type galaxies, therefore, are traditionally believed that they are dynamically simple stellar systems with homogeneous stellar populations (e.g. Gott 1977). The popular Lambda Cold Dark Matter (LCDM) paradigm (e.g. Toomre and Toomre 1972), however, strongly suggested a hierarchical merger picture for massive elliptical galaxies. In this model, early-type galaxies form as a result of major mergers and are thought to have continued star formation. Evidence is growing that a substantial fraction of early-type galaxies has secondary star formation. Furthermore, SAURON survey has revealed a rich diversity in the kinematics, discovering numerous central disks and kinematically decoupled cores (e.g. Emsellem et al. 2004; Sarzi et al. 2006). Early-type galaxies are thus likely to have had complex and varied formation histories.