Cosmicflows-2: SNIa Calibration and H0

TL;DR

This paper calibrates Type Ia supernova distances within the Cosmicflows-2 dataset to estimate the Hubble Constant, achieving a value of approximately 76 km/s/Mpc with associated uncertainties.

Contribution

It introduces a new calibration of SNIa distances anchored by multiple distance indicators, refining the measurement of the Hubble Constant.

Findings

H0 = 75.9 ± 3.8 km s^-1 Mpc^-1

Calibrated SNIa distances using multiple methods

Provides a consistent Hubble Constant estimate within the assumed cosmology.

Abstract

The construction of the Cosmicflows-2 compendium of distances involves the merging of distance measures contributed by the following methods: (Cepheid) Period-Luminosity, Tip of the Red Giant Branch (TRGB), Surface Brightness Fluctuation (SBF), Luminosity-Linewidth (TF), Fundamental Plane (FP), and Type Ia supernova (SNIa). The method involving SNIa is at the top of an interconnected ladder, providing accurate distances to well beyond the expected range of distortions to Hubble flow from peculiar motions. In this paper, the SNIa scale is anchored by 36 TF spirals with Cepheid or TRGB distances, 56 SNIa hosts with TF distances, and 61 groups or clusters hosting SNIa with Cepheid, SBF, TF, or FP distances. With the SNIa scale zero point set, a value of the Hubble Constant is evaluated over a range of redshifts 0.03 < z < 0.5, assuming a cosmological model with Omega_m = 0.27 and Omega_Lambda = 0.73. The value determined for the Hubble Constant is H0 = 75.9 \pm 3.8 km s-1 Mpc-1.