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Galactic structure from trigonometric parallaxes of star-forming regions

Published online by Cambridge University Press:  26 February 2013

Mark J. Reid
Mark J. Reid*
Affiliation:
Harvard–Smithsonian Center for Astrophysics, Cambridge, MA, USA email: reid@cfa.harvard.edu
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Abstract

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Recently, astrometric accuracy approaching ~ 10 μas has become routinely possible with Very Long Baseline Interferometry. Since, unlike at optical wavelengths, interstellar dust is transparent at radio wavelengths, parallaxes and proper motions can now be measured for massive young stars (with maser emission) across the Galaxy, enabling direct measurements of the spiral structure of the Milky Way. Fitting the full 3D position and velocity vectors to a simple model of the Galaxy yields extremely accurate values for its fundamental parameters, including the distance to the Galactic Center, R0=8.38 ± 0.18 kpc, and circular rotation at the Solar Circle, Θ0 = 243 ± 7 km s−1. The rotation curve of the Milky Way, based for the first time on ‘gold standard’ distances and complete 3D information, appears to be very flat.

Keywords

Galaxy: fundamental parametersGalaxy: structureGalaxy: diskHii regionsstars: formation
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S289: Advancing the Physics of Cosmic Distances , August 2012 , pp. 188 - 193
Copyright
Copyright © International Astronomical Union 2013

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