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First Detection of Ammonia in the Large Magellanic Cloud: The Kinetic Temperature of Dense Molecular Cores in N 159 W

Ott, Jürgen and Henkel, Christian and Staveley-Smith, Lister and Weiss, Axel (2010) First Detection of Ammonia in the Large Magellanic Cloud: The Kinetic Temperature of Dense Molecular Cores in N 159 W. Astrophysical Journal, 710 (1). pp. 105-111. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20100217-111118727

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Abstract

The first detection of ammonia (NH_3) is reported from the Magellanic Clouds. Using the Australia Telescope Compact Array, we present a targeted search for the (J, K) = (1,1) and (2,2) inversion lines toward seven prominent star-forming regions in the Large Magellanic Cloud (LMC). Both lines are detected in the massive star-forming region N 159 W, which is located in the peculiar molecular ridge south of 30 Doradus, a site of extreme star formation strongly influenced by an interaction with the Milky Way halo. Using the ammonia lines, we derive a kinetic temperature of ~16 K, which is 2-3 times below the previously derived dust temperature. The ammonia column density, averaged over ~17", is ~6 × 10^(12) cm^(–2) (<1.5 × 10^(13) cm^(–2) over 9" in the other six sources) and we derive an ammonia abundance of ~4 × 10^(–10) with respect to molecular hydrogen. This fractional abundance is 1.5-5 orders of magnitude below those observed in Galactic star-forming regions. The nitrogen abundance in the LMC (~10% solar) and the high UV flux, which can photo-dissociate the particularly fragile NH_3 molecule, both must contribute to the low fractional NH3 abundance, and we likely only see the molecule in an ensemble of the densest, best shielded cores of the LMC.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/710/1/105DOIArticle
http://www.iop.org/EJ/abstract/0004-637X/710/1/105/PublisherArticle
ORCID:
AuthorORCID
Ott, Jürgen0000-0001-8224-1956
Weiss, Axel0000-0003-4678-3939
Additional Information:© 2010 American Astronomical Society. Print publication: Issue 1 (2010 February 10); received 2009 April 23; accepted for publication 2009 November 30; published 2010 January 15. This work has been supported by the National Radio Astronomy Observatory (NRAO) which is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation. We thank the referee for his/her suggestions to improve the paper. Facility: ATCA
Funders:
Funding AgencyGrant Number
National Radio Astronomy ObservatoryUNSPECIFIED
Subject Keywords:galaxies: individual (Large Magellanic Cloud); galaxies: ISM; ISM: molecules; Magellanic Clouds; radio lines: ISM; stars: formation
Issue or Number:1
Record Number:CaltechAUTHORS:20100217-111118727
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20100217-111118727
Official Citation:First Detection of Ammonia in the Large Magellanic Cloud: The Kinetic Temperature of Dense Molecular Cores in N 159 W Jürgen Ott, Christian Henkel, Lister Staveley-Smith, and Axel Weiß 2010 ApJ 710 105-111 doi: 10.1088/0004-637X/710/1/105
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17505
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:17 Feb 2010 21:32
Last Modified:03 Oct 2019 01:29

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