Determination of the Local Hubble Constant from Virgo Infall Using TRGB Distances

Abstract

An independent determination of $H_0$ is crucial given the growing tension between the Hubble constant, $H_0$, derived locally and that determined from the modeling of the cosmic microwave background (CMB) originating in the early universe. In this work, we present a new determination of $H_0$ using velocities and tip of the red giant branch (TRGB) distances to 33 galaxies located between the Local Group and the Virgo cluster. We use a model of the infall pattern of the local Hubble flow modified by the Virgo mass, which is given as a function of the cosmological constants ($H_0$, $Ω_Λ$), the radius of the zero-velocity surface $R_0$, and the intrinsic velocity dispersion, $σ_v$. Fitting velocities and TRGB distances of 33 galaxies to the model, we obtain $H_0 =$ 65.8 $\pm$ 3.5($stat$) $\pm$ 2.4($sys$) km s$^{-1}$ Mpc$^{-1}$ and $R_0 =$ 6.76 $\pm$ 0.35 Mpc. Our local $H_0$ is consistent with the global $H_0$ determined from CMB radiation, showing no tension. In addition, we present new TRGB distances to NGC 4437 and NGC 4592 which are located near the zero-velocity surface: D = 9.28 $\pm$ 0.39 Mpc and D = 9.07 $\pm$ 0.27 Mpc, respectively. Their spatial separation is 0.29$^{+0.30}_{-0.03}$ Mpc, suggesting that they form a physical pair.