The value of the Hubble-Lemaître constant queried by Type Ia Supernovae: A journey from the Calán-Tololo Project to the Carnegie Supernova Program

Abstract: We assess the robustness of the two highest rungs of the "cosmic distance ladder" for Type Ia supernovae and the determination of the Hubble-Lema^itre constant. In this analysis, we hold fixed Rung 1 as the distance to the LMC determined to 1 % using Detached Eclipsing Binary stars. For Rung 2 we analyze two methods, the TRGB and Cepheid distances for the luminosity calibration of Type Ia supernovae in nearby galaxies. For Rung 3 we analyze various modern digital supernova samples in the Hubble flow, such as the Cal\'an-Tololo, CfA, CSP, and Supercal datasets. This metadata analysis demonstrates that the TRGB calibration yields smaller $H_0$ values than the Cepheid calibration, a direct consequence of the systematic difference in the distance moduli calibrated from these two methods. Selecting the three most independent possible methodologies/bandpasses ($B$, $V$, $J$), we obtain $H_{0}=69.9 \pm 0.8$ and $H_{0} =73.5 \pm 0.7$ km s$^{-1}$ Mpc$^{-1}$ from the TRGB and Cepheid calibrations, respectively. Adding in quadrature the systematic uncertainty in the TRGB and Cepheid methods of 1.1 and 1.0 km s$^{-1}$ Mpc$^{-1}$, respectively, this subset reveals a significant 2.0 $\sigma$ systematic difference in the calibration of Rung 2. If Rung 1 and Rung 2 are held fixed, the different formalisms developed for standardizing the supernova peak magnitudes yield consistent results, with a standard deviation of 1.5 km s$^{-1}$ Mpc$^{-1}$, that is, Type Ia supernovae are able to anchor Rung 3 with 2 % precision. This study demonstrates that Type Ia supernovae have provided a remarkably robust calibration of R3 for over 25 years.