The TRGB-SBF Project team is developing an independent distance ladder using a geometrical calibration of the tip of the red giant branch (TRGB) method in elliptical galaxies that can in turn be used to set the surface brightness fluctuation (SBF) distance scale independent of Cepheid variables and Type~Ia supernovae (SNe Ia). The purpose of this project is to measure the local expansion rate of the universe independently of the methods that are most at odds with the theoretically-predicted value of the Hubble-Lema\^itre constant H0, and therefore isolate the influence of potential systematic observational errors. In this paper, we use JWST TRGB distances calibrated using the megamaser galaxy NGC 4258 to determine a new Cepheid-independent SBF zero point for HST. This new calibration, along with improved optical color measurements from PanSTARRS and DECam, gives an updated value of H0=73.8±0.7 (statistical) ±2.3~(systematic) km/s/Mpc that is virtually identical to the SBF Hubble constant measured by Blakeslee et al. 2021.
@article{arxiv.2502.15935,
title = {The TRGB-SBF Project. III. Refining the HST Surface Brightness Fluctuation Distance Scale Calibration with JWST},
author = {Joseph B. Jensen and John P. Blakeslee and Michele Cantiello and Mikaela Cowles and Gagandeep S. Anand and R. Brent Tully and Ehsan Kourkchi and Gabriella Raimondo},
journal= {arXiv preprint arXiv:2502.15935},
year = {2025}
}