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arXiv · 1608.03886

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

M. J. Reid·T. M. Dame
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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.

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M. J. Reid, T. M. Dame. 2016-08-12. On the Rotation Speed of the Milky Way Determined from HI Emission. https://doi.org/10.3847/0004-637x%2F832%2F2%2F159

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