Presentation #315.01 in the session Cosmology.
The Hubble-Lemaitre constant tension is yet an unexplained observation. Distance measurements using Ia supernovae or Cepheids are based on their apparent magnitude, and therefore depend on the rotational velocity of their host galaxies relative to the rotational velocity of the Milky Way. Since the effect of the rotational velocity is expected to be subtle, the rotational velocity of the host galaxies is normally not accounted in analyses of Ho. This study provides empirical evidence showing that the effect of the relative rotational velocity of the host galaxies on the apparent magnitude is not necessarily subtle, and therefore can lead to a small but consistent bias in the estimated distance. Experimental results using SH0ES show that when limiting the data such that all host galaxies rotate in the same direction as the Milky Way, the tension between the Ho determined by Ia supernovae and the Ho determined by the CMB reduces substantially, and becomes statistically insignificant. When using just host galaxies that rotate in the opposite direction relative to the Milky Way, the Ho tension increases. These observations suggest that the rotational velocity of the host galaxies relative to the Milky Way might affect the brightness of Ia supernovae, and consequently affect their estimated distance, leading to a slightly biased Ho.