Clustering of Local Group distances: publication bias or correlated measurements? III. The Small Magellanic Cloud

TL;DR

This paper consolidates various distance measurements to the Small Magellanic Cloud, providing a precise mean distance estimate while discussing potential systematic uncertainties due to complex galaxy geometry and measurement methods.

Contribution

It compiles the largest database of SMC distance estimates and derives a refined mean distance with a comprehensive analysis of systematic effects.

Findings

Mean SMC distance of 18.96 mag with formal error 0.02 mag

Systematic uncertainties may exceed 0.15-0.20 mag due to galaxy complexity

Multiple stellar tracers used for distance estimation

Abstract

Aiming at providing a firm mean distance estimate to the Small Magellanic Cloud (SMC), and thus to place it within the internally consistent Local Group distance framework we recently established, we compiled the current-largest database of published distance estimates to the galaxy. Based on careful statistical analysis, we derive mean distance estimates to the SMC using eclipsing binary systems, variable stars, stellar population tracers, and star cluster properties. Their weighted mean leads to a final recommendation for the mean SMC distance of $(m-M)_0^{\rm SMC} = 18.96 \pm 0.02$ mag, where the uncertainty represents the formal error. Systematic effects related to lingering uncertainties in extinction corrections, our physical understanding of the stellar tracers used, and the SMC's complex geometry---including its significant line-of-sight depth, its irregular appearance which renders definition of the galaxy's center uncertain, as well as its high inclination and possibly warped disk---may contribute additional uncertainties possibly exceeding 0.15--0.20 mag.