THE INFLUENCE OF FAR-ULTRAVIOLET RADIATION ON THE PROPERTIES OF MOLECULAR CLOUDS IN THE 30 DOR REGION OF THE LARGE MAGELLANIC CLOUD

Journal Article · Sun Sep 20 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/703/1/736· OSTI ID:21371969

Pineda, Jorge L; Klein, Ulrich ^[1]; Ott, Juergen ^[2]; Wong, Tony ^[3]; Muller, Erik ^[4]; Hughes, Annie ^[5]

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1. Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)
2. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
3. School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia)
4. Department of Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)
5. Centre for Supercomputing and Astrophysics, Swinburne University of Technology, Hawthorn, VIC 3122 (Australia)

We present a complete {sup 12}CO J = 1 -> 0 map of the prominent molecular ridge in the Large Magellanic Cloud (LMC) obtained with the 22 m ATNF Mopra Telescope. The region stretches southward by {approx}2 deg. (or 1.7 kpc) from 30 Doradus, the most vigorous star-forming region in the Local Group. The location of this molecular ridge is unique insofar as it allows us to study the properties of molecular gas as a function of the ambient radiation field in a low-metallicity environment. We find that the physical properties of CO-emitting clumps within the molecular ridge do not vary with the strength of the far-ultraviolet radiation field. Since the peak CO brightness of the clumps shows no correlation with the radiation field strength, the observed constant value for CO-to-H{sub 2} conversion factor along the ridge seems to require an increase in the kinetic temperature of the molecular gas that is offset by a decrease in the angular filling factor of the CO emission. We find that the difference between the CO-to-H{sub 2} conversion factor in the molecular ridge and the outer Milky Way is smaller than has been reported by previous studies of the CO emission: applying the same cloud identification and analysis methods to our CO observations of the LMC molecular ridge and CO data from the outer Galaxy survey by Dame et al., we find that the average CO-to-H{sub 2} conversion factor in the molecular ridge is X {sub CO} {approx_equal} (3.9 +- 2.5) x 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}, approximately twice the value that we determine for the outer Galaxy clouds. The mass spectrum and the scaling relations between the properties of the CO clumps in the molecular ridge are similar, but not identical, to those that have been established for Galactic molecular clouds.

• OSTI ID: 21371969
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 703; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BRIGHTNESS
ELECTROMAGNETIC RADIATION
EMISSION
FAR ULTRAVIOLET RADIATION
GALAXIES
MAGELLANIC CLOUDS
MASS SPECTRA
MILKY WAY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SPECTRA
STARS
TELESCOPES
ULTRAVIOLET RADIATION