An Outer Arm in the Second Galactic Quadrant: Structure

Abstract

The lack of arm tracers, especially the remote tracers, is one of the most difficult problems preventing us from studying the structure of the Milky Way. Fortunately, with its high-sensitivity CO survey, the Milky Way Imaging Scroll Painting (MWISP) project offers such an opportunity. Since completing about one-third of its mission, an area of l=[100,150] deg, b=[-3,5] deg has nearly been covered. The Outer arm of the Milky Way first clearly revealed its shape in the second galactic quadrant in the form of molecular gas --- this is the first time that the Outer arm has been reported in such a large-scale mapping of molecular gas. Using the 115 GHz 12CO(1-0) data of MWISP at the LSR velocity ~= [-100,-60] km s^-1 and in the area mentioned above, we have detected 481 molecular clouds in total, and among them 332 (about 69\%) are newly detected and 457 probably belong to the Outer arm. The total mass of the detected Outer arm clouds is ~ 3.1*10^6 M_sun. Assuming that the spiral arm is a logarithmic spiral, the pitch angle is fitted as ~ 13.1 deg. Besides combining both the CO data from MWISP and the 21 cm HI data from the Canadian Galactic Plane Survey (CGPS), the gas distribution, warp, and thickness of the Outer arm are also studied.

to be published by ApJS

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Cited by in corpus (18)

• The Milky Way Imaging Scroll Painting (MWISP): Project Details and Initial Results from the Galactic Longitude of 25.8deg to 49.7deg
• The spiral structure of the Milky Way
• A guided map to the Spiral arms in the galactic disk of the Milky Way
• What Does the Milky Way Look Like?
• Tracing the Spiral Structure of the Outer Milky Way with Dense Atomic Hydrogen Gas
• Molecular clouds in the extreme outer Galaxy between $l=34.75^{\circ }$ to $45.25^{\circ }$
• Molecular gas distribution perpendicular to the Galactic plane
• A Morphological Classification of 18190 Molecular Clouds Identified in ${}^{12}$CO Data from the MWISP Survey
• Molecular Clouds in the Second Quadrant of the Milky Way Mid-plane from l$=$104$.{}^{\circ }$75 to l=119$.{}^{\circ }$75 and b=$-$5$.{}^{\circ }$25 to b=5$.{}^{\circ }$25
• The Molecular Structures of Local Arm and Perseus Arm in the Galactic Region of l=[139.75,149.75]${}^{\circ }$, b=[-5.25,5.25]${}^{\circ }$
• Distances to molecular clouds in the second Galactic quadrant
• The Distant Outer Gas Arm Between l=35d and l=45d
• A revised view of the Canis Major stellar overdensity with DECam and Gaia: new evidence of a stellar warp of blue stars
• The Warm-Hot Disk-Halo Interface Below the Perseus Spiral Arm
• A Kinematically Cold Structure of Candidate Young OB Stars Toward The Anticenter
• Measurement of Cosmic-Ray Density in the Spiral Arms toward Galactic Anticenter
• Molecular Clouds at the Edge of the Galaxy II. Physical properties and scaling relations
• Examinations of CO completeness based on three independent CO surveys