TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. IX. THE OUTER ARM IN THE FIRST QUADRANT

• Published in: The Astrophysical journal Vol. 745; no. 1; pp. 82 - 7
• Main Authors: Sanna, A., Reid, M. J., Dame, T. M., Menten, K. M., Brunthaler, A., Moscadelli, L., Zheng, X. W., Xu, Y.
• Format: Journal Article
• Language: English
• Published: Bristol IOP 20.01.2012
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Borders; Earth, ocean, space; Exact sciences and technology; GALAXIES; INCLINATION; MASERS; MASS; ORBITS; Parallax; Pitch angle; Planes; Quadrants; Star formation; STARS; Texts; WATER; Water masers; Galactic planes; Galaxies; Molecular clouds; Galaxy: kinematics and dynamics; Stellar formation region; Pitch angle; Orbits; Astrometry; Massive stars; stars: formation; North galactic pole; Star formation; Dynamics; Masers; Kinematics; Heliocentric distance; Galaxy: fundamental parameters; techniques: high angular resolution
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/745/1/82

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 (ProQuest: Formulae and/or non-USASCII text omitted) 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 super(-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[degrees] for a large section of the arm extending from the first quadrant to the third.