VERY LARGE ARRAY OBSERVATIONS OF THE INFRARED DARK CLOUD G19.30+0.07

Journal Article · Fri May 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/733/1/44· OSTI ID:21576781

Devine, K E; Churchwell, E ^[1]; Chandler, C J; Borg, K J ^[2]; Brogan, C; Indebetouw, R ^[3]; Shirley, Y ^[4]

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1. Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53703 (United States)
2. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
3. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
4. Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)

We present Very Large Array observations of ammonia (NH{sub 3}) (1,1), (2,2), and dicarbon sulfide (CCS) (2{sub 1}-1{sub 0}) emission toward the infrared dark cloud (IRDC) G19.30+0.07 at {approx}22 GHz. The NH{sub 3} emission closely follows the 8 {mu}m extinction. The NH{sub 3} (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of {approx}10-20 K and NH{sub 3} column densities of {approx}10{sup 15} cm{sup -2}. The estimated total mass of G19.30+0.07 is {approx}1130 M{sub sun}. The cloud comprises four compact NH{sub 3} clumps of mass {approx}30-160 M{sub sun}. Two coincide with 24 {mu}m emission, indicating heating by protostars, and show evidence of outflow in the NH{sub 3} 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 NH{sub 3} emission, we find that G19.30+0.07 is composed of three distinct velocity components or 'subclouds'. One velocity component contains the two 24 {mu}m 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 NH{sub 3} and CCS emission from G19.30+0.07 is highly anti-correlated, with the NH{sub 3} 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.

• OSTI ID: 21576781
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 733; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMMONIA
AMPLIFIERS
CLOUDS
DENSITY
DISTRIBUTION
ELECTRONIC EQUIPMENT
EMISSION
EQUIPMENT
EVOLUTION
HYDRIDES
HYDROGEN COMPOUNDS
MASERS
MASS
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PROTOSTARS
SPATIAL DISTRIBUTION
STAR EVOLUTION
VELOCITY
WATER