Spiral structure in the outer Galactic disk. I. The Third Galactic Quadrant

Abstract

We combine optical and radio observations to trace the spiral structure in the Third Quadrant of the Milky Way. The optical observations consist of a large sample of young open clusters and associations, whereas the radio observations consist of a survey of nearby and distant clouds observed in CO. Both the optical and radio samples are the largest ones insofar present in the literature. We use this unique material to analyze the behavior of interstellar extinction and to trace the detailed structure of the Third Galactic Quadrant (TGQ).We find that the Outer (Cygnus) grand design spiral arm is traced by stellar and CO components while the Perseus arm is traced solely by CO and is possibly being disrupted by the crossing of the Local (Orion) arm. The Local arm is traced by CO and young stars toward l = 240 degrees and extends for over 8 kpc along the line of sight reaching the Outer arm. Finally, we characterize the Galactic warp and compare the geometries implied by the young stellar and CO components.

28 pages, 6 eps, somewhat degraded in resolution, figures. Accepted for publication in the Astrophysical Journal

References in corpus (4)

• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• The Spiral Structure of the Outer Milky Way in Hydrogen
• Spiral structure of the Third Galactic Quadrant and the solution to the Canis Major debate
• Photometry of a Galactic field at l = 232, b = -6. The old open cluster Auner 1, the Norma-Cygnus spiral arm and the signature of the warped Galactic Thick Disk

Cited by in corpus (3)

• Searching for spiral features in the outer Galactic disk. The field towards WR38 and WR38a
• Blue Straggler Stars in Galactic Open Clusters and the effect of field star contamination
• Stellar populations in the Canis Major over-density