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 ({{H}} i) gas in the outer Galaxy. Our map has been produced from the Leiden/Argentine/Bonn {{H}} i 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 {{H}} i 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 {{H}} i spiral structure in the outer Galaxy is well described by a four-arm spiral model (pitch angle of 12^\circ ) with some deviations, and gives a new insight into identifying {{H}} i features associated with individual arms.
- Publication:
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Publications of the Astronomical Society of the Pacific
- Pub Date:
- September 2017
- DOI:
- 10.1088/1538-3873/aa7c08
- arXiv:
- arXiv:1706.10084
- Bibcode:
- 2017PASP..129i4102K
- Keywords:
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- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 24 pages, 10 figures, 3 tables