Clustering of Local Group distances: publication bias or correlated measurements? IV. The Galactic Center

TL;DR

This study compiles and analyzes a comprehensive database of Galactic Center distance measurements to derive a well-supported estimate of 8.3 kpc, addressing publication bias and implications for Galactic parameters.

Contribution

It provides the most complete and statistically justified Galactic Center distance estimate by analyzing diverse measurement methods and assessing publication bias.

Findings

Final Galactic Center distance: 8.3 ± 0.2 (stat) ± 0.4 (sys) kpc.

Publication bias appears negligible in centroid-based measurements.

Revisions needed for IAU recommended values of R0 and Θ0.

Abstract

Aiming at deriving a statistically well-justified Galactic Center distance, $R_0$, and reducing any occurrence of publication bias, we compiled the most comprehensive and most complete database of Galactic Center distances available to date, containing 273 new or revised $R_0$ estimates published since records began in October 1918 until June 2016. We separate our $R_0$ compilation into direct and indirect distance measurements. The latter include a large body of estimates that rely on centroid determinations for a range of tracer populations as well as measurements based on kinematic observations of objects at the solar circle, combined with a mass and/or rotational model of the Milky Way. Careful assessment of the Galactic Center distances resulting from orbital modeling and statistical parallax measurements in the Galactic nucleus yields our final Galactic Center distance recommendation of $R_0 = 8.3 \pm 0.2 \mbox{ (statistical)} \pm 0.4 \mbox{ (systematic)}$ kpc. The centroid-based distances are in good agreement with this recommendation. Neither the direct measurements nor the post-1990 centroid-based distance determinations suggest that publication bias may be important. The kinematics-based distance estimates are affected by significantly larger uncertainties, but they can be used to constrain the Galaxy's rotation velocity at the solar Galactocentric distance, $\Theta_0$. Our results imply that the International Astronomical Union-recommended Galactic Center distance ($R_0^{\rm IAU} = 8.5$ kpc) needs a downward adjustment, while its $\Theta_0$ recommendation ($\Theta_0 = 220$ km s$^{-1}$) requires a substantial upward revision.