On the Structure of the Sagittarius Spiral Arm in the Inner Milky Way

Abstract

We report measurements of trigonometric parallax and proper motion for two 6.7 GHz methanol and two 22 GHz water masers located in the far portion of the Sagittarius spiral arm as part of the BeSSeL Survey. Distances for these sources are estimated from parallax measurements combined with 3-dimensional kinematic distances. The distances of G033.64$-$00.22, G035.57$-$00.03, G041.15$-$00.20, and G043.89$-$00.78 are $9.9\pm 0.5$, $10.2\pm 0.6$, $7.6\pm 0.5$, and $7.5\pm 0.3$ kpc, respectively. Based on these measurements, we suggest that the Sagittarius arm segment beyond about 8 kpc from the Sun in the first Galactic quadrant should be adjusted radially outward relative to previous models. This supports the suggestion of Xu et al. (2023) that the Sagittarius and Perseus spiral arms might merge in the first quadrant before spiraling inward to the far end of the Galactic bar.

arXiv comment14 pages, 5 figures, accepted to AJ

References in corpus (24)

• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• The VLA Galactic Plane Survey
• The WISE Catalog of Galactic HII Regions
• The Structure of the Milky Way's Bar Outside the Bulge
• DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments
• A Parallax-based Distance Estimator for Spiral Arm Sources
• Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey
• Trigonometric Parallaxes of Massive Star Forming Regions: I. S 252 & G232.6+1.0
• Trigonometric parallaxes of star forming regions in the Sagittarius spiral arm
• A VLBI Resolution of the Pleiades Distance Controversy
• The First VERA Astrometry Catalog
• The local spiral structure of the Milky Way
• What Does the Milky Way Look Like?
• MultiView High Precision VLBI Astrometry at Low Frequencies
• Trigonometric Parallaxes of Star Forming Regions Beyond the Tangent Point of the Sagittarius Spiral Arm
• Techniques for Accurate Parallax Measurements for 6.7-GHz Methanol Masers
• A Global View on Star Formation: The GLOSTAR Galactic Plane Survey V. 6.7 GHz Methanol Maser Catalogue
• Parallaxes for star forming regions in the inner Perseus spiral arm
• Trigonometric Parallaxes of Four Star-forming Regions in the Distant Inner Galaxy
• Physical conditions around 6.7 GHz methanol masers-I: Ammonia
• Inverse Multview I: Multi-Calibrator inverse phase referencing for Microarcsecond VLBI Astrometry

Cited by in corpus (1)

• Parallax-based Distances to Galactic Hii Regions: Nearby Spiral Structure