On the Rotation Speed of the Milky Way Determined from HI Emission

Abstract

The circular rotation speed of the Milky Way at the solar radius, Theta_o, has been estimated to be 220 km/s by fitting the maximum velocity of HI emission as a function of Galactic longitude. This result is in tension with a recent estimate of Theta_o=240 km/s, based on 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 Theta_o from the HI data when a flat rotation curve is assumed. This relieves the tension between the methods and favors Theta_o=240 km/s.

4 figures

References in corpus (2)

• The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
• Milky Way Kinematics: Measurements at the Subcentral Point of the Fourth Quadrant

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