Tracing the Spiral Structure of the Outer Milky Way with Dense Atomic Hydrogen Gas

Abstract

We present a new face-on map of dense neutral atomic hydrogen (HI) gas in the outer Galaxy. Our map has been produced from the Leiden/Argentine/Bonn (LAB) HI 21-cm line all-sky survey by finding intensity maxima along every line of sight and then by projecting them on the Galactic plane. The resulting face-on map strikingly reveals the complex spiral structure beyond the solar circle, which is characterized by a mixture of distinct long arcs of HI concentrations and numerous 'interarm' features. The comparison with more conventional spiral tracers confirms the nature of those long arc structures as spiral arms. Our map shows that the HI spiral structure in the outer Galaxy is well described by a four-arm spiral model (pitch angle of 12 deg) with some deviations, and gives a new insight into identifying HI features associated with individual arms.

24 pages, 10 figures, 3 tables; accepted for publication in PASP

References in corpus (9)

• The Structure of the Milky Way's Bar Outside the Bulge
• The observed spiral structure of the Milky Way
• The Vertical Structure of the Outer Milky Way HI Disk
• The Spiral Structure of the Outer Milky Way in Hydrogen
• Spiral structure in the outer Galactic disk. I. The Third Galactic Quadrant
• The local spiral structure of the Milky Way
• A Possible Extension of the Scutum-Centaurus Arm into the Outer Second Quadrant
• Characteristics of Spiral Arms in Late-type Galaxies
• On the Rotation Speed of the Milky Way Determined from HI Emission

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