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Arxiv: The Population II Extragalactic Distance Scale: A TRGB Distance to the Fornax Cluster with JWST Published: 5/6/2024 9:00:00 PM Updated: 5/6/2024 9:00:00 PM

Paper abstract: Differences between the local value of the Hubble constant measured via thedistance ladder versus the value inferred from the cosmic microwave backgroundwith the assumption of the standard \LambdaCDM model have reached over5\sigma significance. To determine if this discrepancy is due to new physicsor more mundane systematic errors, it is essential to remove as many sources ofsystematic uncertainty as possible by developing high-precision distanceladders that are independent of the traditional Cepheid and Type Ia supernovaeroute. Here we present JWST observations of three early-type Fornax Clustergalaxies, the first of fourteen observations from a Cycle 2 JWST program. Ourmodest integration times allow us to measure highly precise tip of the redgiant branch (TRGB) distances, and will also be used to perform measurements ofSurface Brightness Fluctuations (SBF). From these three galaxies, we determinean average TRGB distance modulus to the Fornax Cluster of \mu = 31.424 \pm0.077 mag, or D = 19.3 \pm 0.7 Mpc. With eleven more scheduled observationsin nearby elliptical galaxies, our program will allow us set the zero point ofthe SBF scale to better than 2\% for more distant measurements, charting apath towards a high-precision measurement of H_{0} that is independent of thetraditional Cepheid-SN Ia distance ladder.