Astronomy Colloquium

Our understanding of the stellar populations of unresolved galaxies is fundamentally limited by our lack of knowledge of the stellar initial mass function (IMF), and its variation with environment and epoch. In this talk I will present a technique that provides direct measurements of the low-mass IMF (~0.1-1 Msun) in unresolved stellar systems. When this technique is applied to high-quality optical-NIR spectra of nearby early-type galaxies, evidence is found for an IMF that is substantially more "bottom-heavy" than the Galactic IMF. I will also discuss ongoing work aimed at measuring elemental abundances (including C, N, O, Na, Mg, Ca, Ti, Cr, Mn, Fe, Sr, and Ba) of these galaxies, with the goal of constraining their formation histories.