An Update on the Hubble Constant from Surface Brightness Fluctuations

The surface brightness fluctuation (SBF) method is a powerful way to measure distances to evolved galaxies without recent star formation. We have published a value of the Hubble constant using WFC3/IR to measure distances out to 100 Mpc, tied indirectly to a Cepheid calibration. Now, with JWST, the method is capable of reaching several hundred megaparsecs, and we can calibrate it directly using TRGB distances to the same galaxies in which we measure SBF. This provides another precision distance ladder independent of the Cepheid-SNIa ladder. We have received time in both JWST cycles 2 and 3 for this effort, and I will provide an update on progress. I'll also discuss direct comparisons between SBF and SNIa distances.