The TRGB-SBF Project. III. Refining the HST Surface Brightness Fluctuation Distance Scale Calibration with JWST

TL;DR

This paper refines the surface brightness fluctuation distance scale calibration using JWST TRGB distances, leading to a Cepheid-independent Hubble constant measurement consistent with previous SBF results.

Contribution

It introduces a new SBF zero point calibration based on JWST TRGB distances, improving the accuracy of the local Hubble constant measurement.

Findings

New SBF zero point calibrated with JWST TRGB distances.

Updated H_0 value of 73.8 km/s/Mpc with reduced statistical uncertainty.

Results consistent with previous SBF-based Hubble constant measurements.

Abstract

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 $H_0$, 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 $H_0 = 73.8\pm 0.7$ (statistical) $\pm 2.3$~(systematic) km/s/Mpc that is virtually identical to the SBF Hubble constant measured by Blakeslee et al. 2021.