ASTE CO (3-2) MAPPING TOWARD THE WHOLE OPTICAL DISK OF M 83: PROPERTIES OF INTER-ARM GIANT MOLECULAR-CLOUD ASSOCIATIONS

Journal Article · Tue Dec 01 04:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/706/2/1213· OSTI ID:21378114

Muraoka, Kazuyuki; Tosaki, Tomoka; Kuno, Nario; Fukuhara, Masayuki; Kawabe, Ryohei ^[1]; Kohno, Kotaro; Handa, Toshihiro ^[2]; Nakanishi, Kouichiro; Sawada, Tsuyoshi; Ezawa, Hajime ^[3]; Sorai, Kazuo ^[4]; Tanaka, Kunihiko ^[5]

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1. Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)
2. Institute of Astronomy, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
3. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
4. Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)
5. Department of Physics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa (Japan)

We present a new on-the-fly mapping of CO (J = 3-2) line emission with the Atacama Submillimeter Telescope Experiment toward the 8' x 8' (or 10.5 x 10.5 kpc at the distance of 4.5 Mpc) region of the nearby barred spiral galaxy M 83 at an effective resolution of 25''. Due to its very high sensitivity, our CO (J = 3 - 2) map can depict not only spiral arm structures but also spur-like substructures extended in inter-arm regions. This spur-like substructures in CO (J = 3-2) emission are well coincident with the distribution of massive star-forming regions traced by Halpha luminosity and Spitzer/Infrared Array Camera 8 mum emission. We have identified 54 CO (J = 3-2) clumps as Giant Molecular-cloud Associations (GMAs) employing the CLUMPFIND algorithm, and have obtained their sizes, velocity dispersions, virial masses, and CO luminosity masses. We found that the virial parameter alpha, which is defined as the ratio of the virial mass to the CO luminosity mass, is almost unity for GMAs in spiral arms, whereas there exist some GMAs whose alpha are 3-10 in the inter-arm region. We found that GMAs with higher alpha tend not to be associated with massive star-forming regions, while other virialized GMAs are. Since alpha mainly depends on velocity dispersion of the GMA, we suppose that the onset of star formation in these unvirialized GMAs with higher alpha are suppressed by an increase in internal velocity dispersions of giant molecular clouds within these GMAs due to shear motion.

• OSTI ID: 21378114
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 706; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALGORITHMS
CAMERAS
GALAXIES
LUMINOSITY
MASS
MATHEMATICAL LOGIC
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
STARS
TELESCOPES