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Astron. Astrophys. 358, L13-L16 (2000)


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Letter to the Editor

Evidence for a two-armed spiral in the Milky Way

R. Drimmel

Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy (drimmel@to.astro.it)

Received 13 April 2000 / Accepted 26 April 2000

Abstract

Emission profiles of the Galactic plane in K and at [FORMULA] are presented, and features associated with the tangents of the spiral arms are identified. In the K band, which traces stellar emission and suffers little from absorbtion, features associated with the arm tangents indicate that a two-armed logarithmic spiral dominates the nonaxisymmetric structure of the Milky Way. In contrast, the [FORMULA] emission from dust entrained in the interstellar gas is consistent with a four-armed model, in concordance with radio data and optical spiral tracers. This suggests that the non-axisymmetric mass perturbation responsible for the four-armed spiral structure in the gas has a two rather than four-armed structure.

Key words: Galaxy: structure – infrared: galaxies


© European Southern Observatory (ESO) 2000

Online publication: June 26, 2000

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