Event

Distances are the fundamental datum by which we translate observational quantities into astrophysical ones and distances remain difficult to measure. I will describe techniques that use old stellar populations in galaxies to determine distances because old stellar populations exist in all galaxies of all hubble types, in each structural component of a galaxy, and are observable regardless of the galaxy's orientation. Thus, old stellar populations provide a means of reaching galaxies and galaxy structures that are not feasible via the classical Cepheid-based distance ladder. I will describe three techniques: RR Lyrae, tip of the red giant branch stars (TRGB), and surface brightness fluctuations in the context of three specific cosmological applications to which they are suited. These are revealing the detailed hierarchical structure of our own Galaxy via RR Lyrae Stars, measuring the Hubble constant via the TRGB, and building satellite luminosity functions for external galaxies with surface brightness fluctuations. I will honestly present their strengths and weaknesses, with a focus on the published and on-going research projects that will tackle the weaknesses.