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A Distant Extended Spiral Arm in the Fourth Quadrant of the Milky Way
journal contributionposted on 2023-05-16, 19:45 authored by McClure-Griffiths, NM, John DickeyJohn Dickey, Gaensler, BM, Green, AJ
Using data from the Southern Galactic Plane Survey, we present a possible distant spiral arm in the fourth quadrant of the Milky Way. The very distinct and cohesive feature can be traced for over 70Â° as the most extreme positive velocity feature in the longitude-velocity diagram. The feature is at a Galactic radius between 18 and 24 kpc and appears to be the last major structure before the end of the H I disk. We compare the feature with a Galactic spiral model and show that it is well reproduced by a spiral arm of pitch angle i âˆ¼ 9Â°. The arm is quite well confined to the Galactic plane, dropping at most 1 kpc below the Galactic equator. Over most of its length, the arm is 1-2 kpc thick.
Publication titleThe Astrophysical Journal
Department/SchoolSchool of Natural Sciences
PublisherUniversity of Chicago Press
Place of publicationChicago, USA