RESOLVED MEASUREMENTS OF X{sub CO} IN NGC 6946
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States)
- Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
- Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA (United Kingdom)
- Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)
- Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
- National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
- Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
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 {sup 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{sub CO} compared with previous purely interferometric studies. We resolve individual GMCs, measure their luminosities and virial masses, and derive X{sub CO}-the conversion factor from CO measurements to H{sub 2} masses-within individual clouds. On average, we find that X{sub CO} = 1.2 Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -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 {approx}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.
- OSTI ID:
- 22004325
- Journal Information:
- Astrophysical Journal, Vol. 744, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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