Non-Gaussian Error Distribution of Hubble Constant Measurements

Abstract

We construct the error distribution of Hubble constant ($H_0$) measurements from Huchra's compilation of 461 measurements of $H_0$ and the WMAP experiment central value $H_0$ = 71 km s$^{-1}$ Mpc$^{-1}$. This error distribution is non-Gaussian, with significantly larger probability in the tails of the distribution than predicted by a Gaussian distribution. The 95.4 % confidence limits are 7.0 $\sigma$ in terms of the quoted errors. It is remarkably well described by either a widened $n = 2$ Student's $t$ distribution or a widened double exponential distribution. These conclusions are unchanged if we use instead the central value $H_0$ = 67 km s$^{-1}$ Mpc$^{-1}$ found from a median statistics analysis of a major subset of $H_0$ measurements used here.