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The Bones of the Milky Way

Goodman, Alyssa A. and Alves, João and Beaumont, Christopher N. and Benjamin, Robert A. and Borkin, Michelle A. and Burkert, Andreas and Dame, Thomas. M. and Jackson, James and Kauffmann, Jens and Robitaille, Thomas and Smith, Rowan J. (2014) The Bones of the Milky Way. Astrophysical Journal, 797 (1). Art. No. 53. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20150105-093644663

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Abstract

The very long and thin infrared dark cloud "Nessie" is even longer than had been previously claimed, and an analysis of its Galactic location suggests that it lies directly in the Milky Way's mid-plane, tracing out a highly elongated bone-like feature within the prominent Scutum-Centaurus spiral arm. Re-analysis of mid-infrared imagery from the Spitzer Space Telescope shows that this infrared dark cloud (IRDC) is at least two and possibly as many as five times longer than had originally been claimed by Nessie's discoverers; its aspect ratio is therefore at least 300:1 and possibly as large as 800:1. A careful accounting for both the Sun's offset from the Galactic plane (~25 pc) and the Galactic center's offset from the (l^(II), b^(II)) = (0, 0) position shows that the latitude of the true Galactic mid-plane at the 3.1 kpc distance to the Scutum-Centaurus Arm is not b = 0, but instead closer to b = –0.4, which is the latitude of Nessie to within a few parsecs. An analysis of the radial velocities of low-density (CO) and high-density (NH_3) gas associated with the Nessie dust feature suggests that Nessie runs along the Scutum-Centaurus Arm in position-position-velocity space, which means it likely forms a dense "spine" of the arm in real space as well. The Scutum-Centaurus Arm is the closest major spiral arm to the Sun toward the inner Galaxy, and, at the longitude of Nessie, it is almost perpendicular to our line of sight, making Nessie the easiest feature to see as a shadow elongated along the Galactic plane from our location. Future high-resolution dust mapping and molecular line observations of the harder-to-find Galactic "bones" should allow us to exploit the Sun's position above the plane to gain a (very foreshortened) view "from above" the Milky Way's structure.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/797/1/53DOIArticle
http://iopscience.iop.org/0004-637X/797/1/53PublisherArticle
http://arxiv.org/abs/1408.0001arXivArticle
Additional Information:© 2014 American Astronomical Society. Received 2013 December 16; accepted 2014 July 30; published 2014 November 25. A.B. acknowledges support from the Cluster of Excellence “Origin and Structure of the Universe.” A.G. and C.B. thank Microsoft Research, the National Science Foundation (AST- 0908159), and NASA (ADAP NNX12AE11G) for their support. M.B. was supported by the Department of Defense through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program. R.B. acknowledges NASA grant NNX10AI70G.
Funders:
Funding AgencyGrant Number
Cluster of Excellence 'Origin and Structure of the Universe' UNSPECIFIED
Microsoft ResearchUNSPECIFIED
NSFAST-0908159
NASAADAP NNX12AE11G
National Defense Science and Engineering Graduate (NDSEG) FellowshipUNSPECIFIED
NASANNX10AI70G
Subject Keywords:dust, extinction; galaxies: star formation; Galaxy: kinematics and dynamics; Galaxy: structure; ISM: clouds; ISM: kinematics and dynamics; ISM: structure
Record Number:CaltechAUTHORS:20150105-093644663
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150105-093644663
Official Citation:The Bones of the Milky Way Alyssa A. Goodman et al. 2014 ApJ 797 53
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53166
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:05 Jan 2015 18:04
Last Modified:12 Jun 2015 19:06

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