The Complete Sample of Available SNe Ia Luminosity Calibrations from the TRGB Observed with either HST or JWST

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Abstract Distance ladders, which calibrate the luminosity of Type Ia supernovae (SNe Ia), currently provide the strongest constraints on the local value of H 0 . Recent studies from the Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) show good consistency between measurements of SNe Ia host distances. These are calibrated to NGC 4258 using different primary distance indicators (Cepheids, Tip of the Red Giant Branch or TRGB), J-region Asymptotic Giant Branch, and Miras). However, some subsamples of calibrated SNe Ia employed to measure H 0 yield noteworthy differences due to small sample statistics, but also due to differences in sample selection. This issue is particularly important for TRGB-derived calibrations owing to the smaller volume they reach compared to Cepheids, reducing sample size and enhancing the size of statistical fluctuations. To mitigate this issue, we compile the largest and complete (as currently available) sample of HST or JWST measurements of the TRGB in the hosts of normal SNe Ia for a total of N = 35, 50% larger than the previous largest. Most are present in the literature, and we compile multiple measures when available. We also add 5 SNe Ia hosts from the HST archive, not previously published. The full sample together with the Pantheon+ SN catalog gives H 0 = 72.1–73.3 ± 1.8 km s −1 Mpc −1 (depending on methodology), in good agreement with the value of 72.5 ± 1.5 km s −1 Mpc −1 from HST Cepheids in hosts of 42 SNe Ia calibrated by the same anchor, NGC 4258. We trace the difference in the result of H 0 = 70.4 ± 1.9 km s −1 Mpc −1 from W. L. Freedman et al. to 11 hosts not selected for that CCHP compilation (of N = 24), which alone yield H 0 = 74.1 km s −1 Mpc −1 , 2 σ higher than the selected sample. A smaller increase of 0.6 km s −1 Mpc −1 comes from a commonly employed correction for peculiar velocities.

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