AR 16122 (Archival Research)

Sun Jul 14 04:10:47 GMT 2024

Principal Investigator: Meredith Durbin
PI Institution: University of California - Berkeley
Investigators (xml)

Title: A Fully Self-Consistent Local Group NIR-TRGB Calibration
Cycle: 28

Upcoming high-resolution observing facilities will enable direct measurements of distances in the Hubble flow that are fully independent of other standard candles via the tip of the red giant branch (TRGB). These facilities (JWST, WFIRST, ELTs, and others) will perform optimally in the near-infrared, where the behavior of the TRGB remains unevenly characterized. To fully exploit future capabilities, we require a thorough characterization of the NIR TRGB with archival data. We propose to use archival F814W, F110W, and F160W observations of IC 1613, M31, and M33 to perform the first fully empirical, fully self-consistent calibration of the HST NIR-TRGB color-magnitude relation to date, including rigorous tests of potential systematics. Existing observations of M31 and M33 in particular provide unparalleled laboratories for performing this study, as they span a wide range of relevant characteristics such as ages, metallicities, surface densities, and dust geometries -- all of which can affect the NIR TRGB's measured luminosity in complex and subtle ways. This work will provide a necessary complement to current NIR-TRGB studies that focus on more distant targets, and will lay critical groundwork for the next generation of distance scale measurements.