LUMINOUS INFRARED GALAXIES WITH THE SUBMILLIMETER ARRAY. III. THE DENSE KILOPARSEC MOLECULAR CONCENTRATIONS OF Arp 299
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 Canada (Canada)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- University of Helsinki Observatory (Finland)
- Academia Sinica Institute of Astronomy and Astrophysics, Taipei 106, Taiwan (China)
- Joint ALMA Office, Avda El Golf 40, piso 18, Santiago, Chile 7550108 (Chile)
We have used high-resolution ({approx}2.''3) observations of the local (D{sub L} = 46 Mpc) luminous infrared galaxy Arp 299 to map out the physical properties of the molecular gas that provides the fuel for its extreme star formation activity. The {sup 12}CO J = 3-2, {sup 12}CO J = 2-1, and {sup 13}CO J = 2-1 lines were observed with the Submillimeter Array, and the short spacings of the {sup 12}CO J = 2-1 and J = 3-2 observations have been recovered using the James Clerk Maxwell Telescope single dish observations. We use the radiative transfer code RADEX to estimate the physical properties (density, column density, and temperature) of the different regions in this system. The RADEX solutions of the two galaxy nuclei, IC 694 and NGC 3690, are consistent with a wide range of gas components, from warm moderately dense gas with T{sub kin} > 30 K and n(H{sub 2}) {approx} 0.3-3 Multiplication-Sign 10{sup 3} cm{sup -3} to cold dense gas with T{sub kin} {approx} 10-30 K and n(H{sub 2}) > 3 Multiplication-Sign 10{sup 3} cm{sup -3}. The overlap region is shown to have a better constrained solution with T{sub kin} {approx} 10-50 K and n(H{sub 2}) {approx} 1-30 Multiplication-Sign 10{sup 3} cm{sup -3}. We estimate the gas masses and star formation rates of each region in order to derive molecular gas depletion times. The depletion times of all regions (20-50 Myr) are found to be about two orders of magnitude lower than those of normal spiral galaxies. This rapid depletion time can probably be explained by a high fraction of dense gas on kiloparsec scales in Arp 299. We estimate the CO-to-H{sub 2} factor, {alpha}{sub co} to be 0.4 {+-} 0.3(3 Multiplication-Sign 10{sup -4}/x{sub CO}) M{sub Sun} (K km s{sup -1} pc{sup 2}){sup -1} for the overlap region. This value agrees well with values determined previously for more advanced merger systems.
- OSTI ID:
- 22036918
- Journal Information:
- Astrophysical Journal, Vol. 753, 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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