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Trigonometric Parallaxes of Massive Star-forming Regions. IX. The Outer Arm in the First Quadrant

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Abstract

  • We report a trigonometric parallax measurement with the Very Long Baseline Array for the water maser in the distant high-mass star-forming region G75.30 1.32. This source has a heliocentric distance of 9.25 0.45 - 0.40 kpc, which places it in the Outer arm in the first Galactic quadrant. It lies 200 pc above the Galactic plane and is associated with a substantial H I enhancement at the border of a large molecular cloud. At a Galactocentric radius of 10.7 kpc, G75.30 1.32 is in a region of the Galaxy where the disk is significantly warped toward the North Galactic Pole. While the star-forming region has an instantaneous Galactic orbit that is nearly circular, it displays a significant motion of 18 km s-1 toward the Galactic plane. The present results, when combined with two previous maser studies in the Outer arm, yield a pitch angle of about 12° for a large section of the arm extending from the first quadrant

Publication Date

  • 2012

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