Very Large Array Observations of the Infrared Dark Cloud G19.30+0.07

Type Journal Article
Names K. E. Devine, C. J. Chandler, C. Brogan, E. Churchwell, R. Indebetouw, Y. Shirley, K. J. Borg
Publication The Astrophysical Journal
Volume 733
Issue 1
Pages 44
Date May 1, 2011
URL http://adsabs.harvard.edu/abs/2011ApJ...733...44D
Library Catalog NASA ADS
Abstract We present Very Large Array observations of ammonia (NH3) (1,1), (2,2), and dicarbon sulfide (CCS) (21-10) emission toward the infrared dark cloud (IRDC) G19.30+0.07 at ~22 GHz. The NH3 emission closely follows the 8 μm extinction. The NH3 (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of ~10-20 K and NH3 column densities of ~1015 cm-2. The estimated total mass of G19.30+0.07 is ~1130 M sun. The cloud comprises four compact NH3 clumps of mass ~30-160 M sun. Two coincide with 24 μm emission, indicating heating by protostars, and show evidence of outflow in the NH3 emission. We report a water maser associated with a third clump; the fourth clump is apparently starless. A non-detection of 8.4 GHz emission suggests that the IRDC contains no bright H II regions and places a limit on the spectral type of an embedded zero-age main-sequence star to early-B or later. From the NH3 emission, we find that G19.30+0.07 is composed of three distinct velocity components or "subclouds." One velocity component contains the two 24 μm sources and the starless clump, another contains the clump with the water maser, while the third velocity component is diffuse, with no significant high-density peaks. The spatial distribution of NH3 and CCS emission from G19.30+0.07 is highly anti-correlated, with the NH3 predominantly in the high-density clumps and the CCS tracing lower-density envelopes around those clumps. This spatial distribution is consistent with theories of evolution for chemically young low-mass cores, in which CCS has not yet been processed to other species and/or depleted in high-density regions.
Tags ISM: MOLECULES, ISM: clouds, Radio Lines: ISM, STARS: FORMATION
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