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The Influence of Far-Ultraviolet Radiation on the Properties of Molecular Clouds in the 30 Dor Region of the Large Magellanic Cloud

Pineda, Jorge L. and Ott, Jürgen and Klein, Ulrich and Wong, Tony and Muller, Erik and Hughes, Annie (2009) The Influence of Far-Ultraviolet Radiation on the Properties of Molecular Clouds in the 30 Dor Region of the Large Magellanic Cloud. Astrophysical Journal, 703 (1). pp. 736-751. ISSN 0004-637X.

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We present a complete ^(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 ~2° (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_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_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_2 conversion factor in the molecular ridge is X_(CO) ≃ (3.9 ± 2.5) × 10^(20) cm^(–2) (K km s^(–1))^(–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.

Item Type:Article
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Pineda, Jorge L.0000-0001-8898-2800
Ott, Jürgen0000-0001-8224-1956
Additional Information:© 2009 American Astronomical Society. Print publication: Issue 1 (2009 September 20); received 2008 December 19; accepted for publication 2009 July 27; published 2009 September 1. This work was supported by the Deutsche Forschungs Gemeinschaft (DFG) via Grant SFB 494. We thank Frank Israel for providing the SEST data set used to check the calibration of our data, Thomas Dame for providing the 2nd Quadrant data set, and Erik Rosolowsky for helping us with CLOUDPROPS, used to check our GAUSSCLUMPS decomposition, and with the error-invariables procedure. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We made use of the NASA/IPAC/IRAS/HiRES data reduction facilities. This research has made use of NASA’s Astrophysics Data System Abstract Service.
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)SFB 494
Subject Keywords:galaxies: ISM; ISM: molecules; ISM: structure; Magellanic Clouds
Issue or Number:1
Record Number:CaltechAUTHORS:20090925-115010461
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Official Citation:The Influence of Far-Ultraviolet Radiation on the Properties of Molecular Clouds in the 30 Dor Region of the Large Magellanic Cloud Jorge L. Pineda, Jürgen Ott, Ulrich Klein, Tony Wong, Erik Muller, and Annie Hughes 2009 ApJ 703 736-751 doi: 10.1088/0004-637X/703/1/736
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16062
Deposited By: Jason Perez
Deposited On:28 Sep 2009 20:38
Last Modified:09 Mar 2020 13:19

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