12:00–1:00 pm ERC 401
Meredith Durbin (University of Washington) "Nailing the Near-IR Tip of the Red Giant Branch with HST: Status, Prospects, and Challenges"
I will discuss the calibration status of the tip of the red giant branch (TRGB) in the near-infrared with HST. First, I will present a method for measuring the multiwavelength TRGB using extreme deconvolution (XDGMM), which enables self-consistent color and magnitude measurements across multiple bandpasses and accounts for photometric uncertainties and color-magnitude covariance. I will demonstrate this method's application to a re-reduction of optical and near-IR HST data of 22 Local Volume (~2-4 Mpc) galaxies, and compare several possible absolute calibrations of the resulting TRGB measurements. Calibrations based on two widely used suites of model isochrones are systematically offset from each other at the ~0.15 mag level, and are internally inconsistent with observed optical-NIR colors as well. I will then discuss some of my recent work on characterizing sources of uncertainty in empirical NIR-TRGB studies, including reconciliation of ground- and space-based measurements, the effects of dust and other contaminants, and low-level photometry systematics.
