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Resolved Measurements of X_(CO) in NGC 6946

Donovan Meyer, Jennifer and Koda, Jin and Momose, Rieko and Fukuhara, Masayuki and Mooney, Thomas and Towers, Sarah and Egusa, Fumi and Kennicutt, Robert and Kuno, Nario and Carty, Misty and Sawada, Tsuyoshi and Scoville, Nick (2012) Resolved Measurements of X_(CO) in NGC 6946. Astrophysical Journal, 744 (1). p. 42. ISSN 0004-637X.

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We present the largest sample to date of giant molecular clouds (GMCs) in a substantial spiral galaxy other than the Milky Way. We map the distribution of molecular gas with high resolution and image fidelity within the central 5 kpc of the spiral galaxy NGC 6946 in the ^(12)CO (J = 1-0) transition. By combining observations from the Nobeyama Radio Observatory 45 m single dish telescope and the Combined Array for Research in Millimeter Astronomy interferometer, we are able to obtain high image fidelity and accurate measurements of L_CO compared with previous purely interferometric studies. We resolve individual GMCs, measure their luminosities and virial masses, and derive X CO—the conversion factor from CO measurements to H2 masses—within individual clouds. On average, we find that X_CO = 1.2 × 10^(20) cm^(–2) (K km s^(–1))^(–1), which is consistent within our uncertainties with previously derived Galactic values as well as the value we derive for Galactic GMCs above our mass sensitivity limit. The properties of our GMCs are largely consistent with the trends observed for molecular clouds detected in the Milky Way disk, with the exception of six clouds detected within ~400 pc of the center of NGC 6946, which exhibit larger velocity dispersions for a given size and luminosity, as has also been observed at the Galactic center.

Item Type:Article
Related URLs:
URLURL TypeDescription
Donovan Meyer, Jennifer0000-0002-3106-7676
Koda, Jin0000-0002-8762-7863
Kennicutt, Robert0000-0001-5448-1821
Scoville, Nick0000-0002-0438-3323
Additional Information:© 2012 American Astronomical Society. Received 2011 July 26; accepted 2011 September 23; published 2011 December 13. The authors thank the anonymous referee for the suggestions which improved the discussion of this paper. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:galaxies: individual (NGC 6946); galaxies: ISM; ISM: molecules
Issue or Number:1
Record Number:CaltechAUTHORS:20120127-095628659
Persistent URL:
Official Citation:Resolved Measurements of X CO in NGC 6946 Jennifer Donovan Meyer et al. 2012 ApJ 744 42
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28994
Deposited By: Jason Perez
Deposited On:30 Jan 2012 15:38
Last Modified:09 Mar 2020 13:18

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