RESOLVED GIANT MOLECULAR CLOUDS IN NEARBY SPIRAL GALAXIES: INSIGHTS FROM THE CANON CO (1-0) SURVEY
- 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)
- Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
- Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA (United Kingdom)
- Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano, 384-1305 (Japan)
- Astronomy Department, University of Illinois, Urbana, IL 61801 (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 resolve 182 individual giant molecular clouds (GMCs) larger than 2.5 Multiplication-Sign 10{sup 5} M{sub Sun} in the inner disks of 5 large nearby spiral galaxies (NGC 2403, NGC 3031, NGC 4736, NGC 4826, and NGC 6946) to create the largest such sample of extragalactic GMCs within galaxies analogous to the Milky Way. Using a conservatively chosen sample of GMCs most likely to adhere to the virial assumption, we measure cloud sizes, velocity dispersions, and {sup 12}CO (J = 1-0) luminosities and calculate cloud virial masses. The average conversion factor from CO flux to H{sub 2} mass (or X{sub CO}) for each galaxy is 1-2 Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}, all within a factor of two of the Milky Way disk value ({approx}2 Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}). We find GMCs to be generally consistent within our errors between the galaxies and with Milky Way disk GMCs; the intrinsic scatter between clouds is of order a factor of two. Consistent with previous studies in the Local Group, we find a linear relationship between cloud virial mass and CO luminosity, supporting the assumption that the clouds in this GMC sample are gravitationally bound. We do not detect a significant population of GMCs with elevated velocity dispersions for their sizes, as has been detected in the Galactic center. Though the range of metallicities probed in this study is narrow, the average conversion factors of these galaxies will serve to anchor the high metallicity end of metallicity-X{sub CO} trends measured using conversion factors in resolved clouds; this has been previously possible primarily with Milky Way measurements.
- OSTI ID:
- 22121795
- Journal Information:
- Astrophysical Journal, Vol. 772, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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