Reid, M. J. and Dame, T. M. 2016. "On the Rotation Speed of the Milky Way Determined from H i Emission." The Astrophysical Journal 832:159. https://doi.org/10.3847/0004-637X/832/2/159
Overview
abstract
The circular rotation speed of the Milky Way at the solar radius, T0, has been estimated to be 220 km s-1 by fitting the maximum velocity of H i emission as a function of Galactic longitude. This result is in tension with a recent estimate of T0 = 240 km s-1, based on Very Long Baseline Interferometry (VLBI) parallaxes and proper motions from the BeSSeL and VERA surveys for large numbers of high-mass star-forming regions across the Milky Way. We find that the rotation curve best fitted to the VLBI data is slightly curved, and that this curvature results in a biased estimate of T0 from the H i data when a flat rotation curve is assumed. This relieves the tension between the methods and favors T0 = 240 km s-1.
