An improved Tully–Fisher estimate of H₀

Abstract

We propose an improved comprehensive method for determining the Hubble constant (H0) using the Tully–Fisher relation. By fitting a peculiar velocity model in conjunction with the Tully–Fisher relation, all available data can be used to derive self-consistent Tully–Fisher parameters. In comparison to previous approaches, our method offers several improvements: it can be readily generalized to different forms of the Tully–Fisher relation and its intrinsic scatter; it uses a peculiar velocity model to predict distances more accurately; it can account for all selection effects; it uses the entire data set to fit the Tully–Fisher relation; and it is fully self-consistent. The Tully–Fisher relation zero-point is calibrated using the subset of galaxies with distances from absolute distance indicators. We demonstrate this method on the Cosmicflows-4 catalogue i-band and W1-band Tully–Fisher samples and show that the uncertainties from fitting the Tully–Fisher relation amount to only 0.2 km s−1 Mpc−1. Using all available absolute distance calibrators, we obtain H0 = 73.3 ± 2.1 (stat) ± 3.5 (sys) km s−1 Mpc−1, where the statistical uncertainty is dominated by the small number of galaxies with absolute distance estimates. The substantial systematic uncertainty reflects inconsistencies between various zero-point calibrations of the Cepheid period–luminosity relation, the tip of the red giant branch standard candle, and the Type Ia supernova standard candle. However, given a reliable set of absolute distance calibrators, our method promises enhanced precision in H0 measurements from large new Tully–Fisher samples such as the WALLABY survey.