The New Era in Stellar Population Synthesis: Methods & 50362 Applications

The study of the stellar content of distant galaxies has a long and venerable history but, at the same time, something of a 'bad reputation' due to the numerous problems associated with dificulties in disentagling age, metallicity and extinction effects. I'll discuss recent developments in the field. In particular, I'll show how modeling the full spectrum (instead of a handfull of "pet" indices,as I and many others did in the past) helps a lot in removing such degeneracies. The modelling process, nevertheless, involves daunting computational tasks in high-dimensional spaces, so smart techniques are needed to explore the huge parameter space.

In past year or so we have developed a population synthesis code (STARLIGHT) whose power far surpasses original expectations. I'll present this technique and applications ranging from low-luminosity AGN, Seyfert nuclei, luminous IR and normal galaxies, with emphasis on recent results obtained for ~ 50k galaxies from the SDSS. I'll show how, besides providing excelent fits to observed spectra, STARLIGHT recovers astrophysical sound results, such as strong correlations between stellar and nebular extinction, stellar and nebular metallicities, stellar mass and velocity dispersion, age and mass, etc... As it will become clear, the problem nowadays is not so much how to retrieve physical properties from galaxy spectra but how to make sense of so much information!