Median Statistics Estimate of the Galactic Rotational Velocity

Abstract

We compile a complete collection of 19 recent (since 2000) measurements of $\Theta_0$, the rotational velocity of the Milky Way at $R_0$ (the radial distance of the Sun from the Galactic center). These measurements use tracers that are believed to more accurately reflect the systematic rotation of the Milky Way. Unlike other recent compilations of $\Theta_0$, our collection includes only independent measurements. We find that these 19 measurements are distributed in a mildly non-Gaussian fashion and a median statistics estimate indicates $\Theta_0 = 220\ \pm 10$ km\,s$^{-1}$ (2$\sigma$ error) as the most reliable summary, at $R_0 = 8.0 \pm 0.3$ kpc (2$\sigma$ error).