Two New Determinations of the Hubble Constant via the Classical Distance Ladder

I will discuss two new studies that each check an independent, major aspect of distance ladder Hubble constant (H0) experiments: 1) the measurement of extragalactic distances to SN host galaxies, and 2) the analysis of SN light curves and resultant cosmological inference. In the first study, new JWST measurements of three independent extragalactic distance indicators were used to evaluate each method's performance and provide new constraints on H0. Two of the three methods–the tip of the red giant branch (TRGB) and a carbon-enhanced population of asymptotic giant branch stars (or JAGB)–were found to agree to <1% in distance and yielded values of H0 equal to 69 km/s/Mpc. Our third analysis based on Cepheids, however, yielded a value near 72 km/s/Mpc, which is in better agreement with the SH0ES constraint of 73 that is also based on Cepheid distances. The Cepheids turning out to be the "odd method out" could be signaling the presence of a yet undiscovered systematic unique to the method, one which may account for a significant portion of the Hubble Tension. In the second study I will discuss, we focus on an independent analysis of the SNe using the Union+Unity hierarchical Bayesian framework for SN cosmology inference. Already used to constrain redshift-dependent cosmological parameters such as w/w_a, we have now updated Unity to include nearby SNe and have a (currently blinded) 1.5% constraint on H0. It is likely we will have an unblinded result by the time of this talk.