UV Excess and AGB Evolution in Elliptical-Galaxy Stellar Populations

Abstract

Summary. The puzzling origin of the "UV-upturn" phenomenon, observed in some elliptical galaxies, has recently been settled by identifying hot HB stars as main contributors to galaxy ultraviolet luminosity excess. While a blue HB morphology seems a natural characteristic of metal-poor stellar populations, its appearence in metal-rich systems, often coupled with a poorer rate of planetary nebulae per unit galaxy luminosity, might be calling for an intimate connection between UV excess and AGB properties in early-type galaxies. In this work, we want to briefly assess this issue relying on infrared surface brightness fluctuactions as a powerful tool to trace AGB properties in external galaxies with unresolved stellar populations.