CfA OIR Division Lunch Talks
Wednesday, October 22, 2008, 11:00 am, Pratt Conference Room (PG-04)

New Constraints on the History of Star Formation of Early Type Galaxies
Dr. Ricardo Schiavon (Gemini)

More than half of the stellar mass in the universe today is contained in early-type galaxies, yet we don't know how these objects were assembled. One of the best ways of constraining models for the genesis of galaxies is to study when their stars were formed. I will briefly describe how the method of stellar population synthesis is used to help unveiling the history of star formation of galaxies. This will be followed by a presentation of results from the analysis of high quality spectra of early type galaxies in the local (SDSS) and distant (DEEP2) universe, using my accurate stellar population synthesis models, which can be used to constrain the abundance pattern of stars in early-type galaxies, as well as their age distribution. Evidence from stellar ages and abundances indicates that: 1) the bulk of the stellar mass in early-type galaxies was formed in a star formation event that happened before z ~ 1.5, and which lasted between 200 and 1,000 Myr; 2) a small fraction of the stellar mass in early-type galaxies is made of young/intermediate stars. indicating that star formation in these systems hasn't ceased from z ~ 1 to the present day. I will conclude by briefly describing APOGEE, the Apache Point Observatory Galactic Evolution Experiment, which is one of four SDSS-III surveys, aimed at studying the stellar populations of our own Galaxy. APOGEE will obtain high resolution H-band spectra of 100,000 stars, and is likely to bring about a paradigm change in our understanding of the formation of the Galaxy.