On the Spiral Structure of the Milky Way Galaxy

Abstract

We consider the possible pattern of the overall spiral structure of the Galaxy, using data on the distribution of neutral (atomic), molecular, and ionized hydrogen, on the base of the hypothesis of the spiral structure being symmetric, i.e. the assumption that spiral arms are translated into each other for a rotation around the galactic center by 180° (a two-arm pattern) or by 90° (a four-arm pattern). We demonstrate that, for the inner region, the observations are best represented with a four-arm scheme of the spiral pattern, associated with all-Galaxy spiral density waves. The basic position is that of the Carina arm, reliably determined from distances to HII regions and from HI and H2 radial velocities. This pattern is continued in the quadrants III and IV with weak outer HI arms; from their morphology, the Galaxy should be considered an asymmetric multi-arm spiral. The kneed shape of the outer arms that consist of straight segments can indicate that these arms are transient formations that appeared due to a gravitational instability in the gas disk. The distances between HI superclouds in the two arms that are the brightest in neutral hydrogen, the Carina arm and the Cygnus (Outer) arm, concentrate to two values, permitting to assume the presence of a regular magnetic field in these arms.

21 pages, 14 fugures; accepted for publication in Astronomichesky Journal (Astron. Rep.)

References in corpus (10)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• The Spiral Structure of the Outer Milky Way in Hydrogen
• Kinematics of Spiral Arm Streaming in M51
• Discovery of a relationship between spiral arm morphology and supermassive black hole mass in disk galaxies
• The long Galactic bar as seen by UKIDSS Galactic Plane Survey
• Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. I. Method outline
• Simulations of spiral galaxies with an active potential: molecular cloud formation and gas dynamics
• Star formation bursts in isolated spiral galaxies
• The Warp and Spiral Arms of the Milky Way
• Star-Forming Complexes in Galaxies

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