Stretch to stretch, dust to dust: Lower-value local H_0 measurements from the two-population modelling of type Ia supernovae

Vol. 702
3. Cosmology (including clusters of galaxies)

Stretch to stretch, dust to dust: Lower-value local H_0 measurements from the two-population modelling of type Ia supernovae

Thanks to improvements in the precision and accuracy of measurements, there now exists a discrepancy between the two values of the Hubble constant (H0): the local one, measured empirically from standard candles, and that derived from the standard model at early epochs and cosmic microwave background measurements. The authors revisit the local Hubble constant measurement from type Ia supernovae calibrated with Cepheids by modeling the differences between the two stellar populations, both intrinsic and due to dust. The calibration of supernovae includes the stretch of their light curves and possible obscuration by dust.

After careful modeling and taking the broadening and reddening of the different populations of supernovae into account, the mean extinction is found to be consistent with the Milky Way-like interstellar dust model, and is substantially higher than the value used in previous supernova calibrations. This leads to a new H0 of 70.59 +- 1.15 km/s/Mpc, or a more conservative choice of 71.45+-1.03 km/s/Mpc. This study thus reduces the Ho tension by at least 30 per cent and up to 50 per cent.