Clustering of Local Group distances: publication bias or correlated measurements? II. M31 and beyond

TL;DR

This paper consolidates and refines distance measurements to Local Group galaxies, especially M31, by analyzing published data to establish a consistent and unbiased distance scale for nearby galaxies.

Contribution

It extends previous work on publication bias to include M31, M33, and dwarf galaxies, providing a homogeneous set of distance moduli based on multiple stellar tracers.

Findings

Recommended M31 distance modulus: 24.46 ± 0.10 mag

Derived a consistent set of benchmark distances for Local Group galaxies

Established a robust local extragalactic distance ladder

Abstract

The accuracy of extragalactic distance measurements ultimately depends on robust, high-precision determinations of the distances to the galaxies in the local volume. Following our detailed study addressing possible publication bias in the published distance determinations to the Large Magellanic Cloud (LMC), here we extend our distance range of interest to include published distance moduli to M31 and M33, as well as to a number of their well-known dwarf galaxy companions. We aim at reaching consensus on the best, most homogeneous, and internally most consistent set of Local Group distance moduli to adopt for future, more general use based on the largest set of distance determinations to individual Local Group galaxies available to date. Based on a careful, statistically weighted combination of the main stellar population tracers (Cepheids, RR Lyrae variables, and the magnitude of the tip of the red-giant branch), we derive a recommended distance modulus to M31 of $(m-M)_0^{\rm M31} = 24.46 \pm 0.10$ mag---adopting as our calibration an LMC distance modulus of $(m-M)_0^{\rm LMC} = 18.50$ mag---and a fully internally consistent set of benchmark distances to key galaxies in the local volume, enabling us to establish a robust and unbiased, near-field extragalactic distance ladder.