ON THE NATURE OF THE LOCAL SPIRAL ARM OF THE MILKY WAY
- Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)
- Nanjing University, Nanjing 20093 (China)
Trigonometric parallax measurements of nine water masers associated with the Local Arm of the Milky Way were carried out as part of the BeSSeL Survey using the Very Long Baseline Array. When combined with 21 other parallax measurements from the literature, the data allow us to study the distribution and three-dimensional motions of star forming regions in the spiral arm over the entire northern sky. Our results suggest that the Local Arm does not have the large pitch angle characteristic of a short spur. Instead its active star formation, overall length (>5 kpc), and shallow pitch angle ({approx}10 Degree-Sign ) suggest that it is more like the adjacent Perseus and Sagittarius Arms; perhaps it is a branch of one of these arms. Contrary to previous results, we find the Local Arm to be closer to the Perseus than to the Sagittarius Arm, suggesting that a branching from the former may be more likely. An average peculiar motion of near zero toward both the Galactic center and north Galactic pole, and counter rotation of {approx}5 km s{sup -1} were observed, indicating that the Local Arm has similar kinematic properties as found for other major spiral arms.
- OSTI ID:
- 22126665
- Journal Information:
- Astrophysical Journal, Vol. 769, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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