case western reserve university



Cool Insights into Early-Type Galaxies

David Silva (ESO)

The rest-frame K-band flux from early-type galaxies E/S0 galaxies arises mainly from cool, evolved stars near or above the tip of the red giant branch. With various collaborators, I am exploring new ways of using these stars to constrain the stellar age and metallicity distributions in early-type galaxies. In a series of papers by Rejkuba, Minniti, Silva, and Bedding, we have shown that multi-year observations of LPVs can provide interesting constraints on stellar age distributions in resolved systems. In unresolved systems, Kuntschner and I are using age-insensitive spectral features in the K-band to study how mean metallicity (and perhaps relative abundance) changes between galaxies as well as within individual galaxies. Furthermore, comparing the behavior of these features to the behavior of the (infamous) Lick indices may help us disentangle age-metallicity degeneracy in the Lick indices. Both projects facilitate similar studies in more distant galaxies in the JWST and ELT era. In this talk, I present recent results and on-going work based on observations obtained at the ESO Very Large Telescope.