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Title: DISTINCT CHEMICAL REGIONS IN THE ''PRESTELLAR'' INFRARED DARK CLOUD G028.23-00.19

We have observed the Infrared Dark Cloud (IRDC) G028.23-00.19 at 3.3 mm using the Combined Array for Research in Millimeter-wave Astronomy. In its center, the IRDC hosts one of the most massive ({approx}1520 M{sub Sun }) quiescent, cold (12 K) clumps known (MM1). The low temperature, high NH{sub 2}D abundance, narrow molecular line widths, and absence of embedded infrared sources (from 3.6 to 70 {mu}m) indicate that the clump is likely prestellar. Strong SiO emission with broad line widths (6-9 km s{sup -1}) and high abundances ((0.8-4) Multiplication-Sign 10{sup -9}) is detected in the northern and southern regions of the IRDC, unassociated with MM1. We suggest that SiO is released to the gas phase from the dust grains through shocks produced by outflows from undetected intermediate-mass stars or clusters of low-mass stars deeply embedded in the IRDC. A weaker SiO component with narrow line widths ({approx}2 km s{sup -1}) and low abundances (4.3 Multiplication-Sign 10{sup -11}) is detected in the center-west region, consistent with either a ''subcloud-subcloud'' collision or an unresolved population of a few low-mass stars. We report widespread CH{sub 3}OH emission throughout the whole IRDC and the first detection of extended narrow methanol emission ({approx}2 km s{sup -1})more » in a cold, massive prestellar clump (MM1). We suggest that the most likely mechanism releasing methanol into the gas phase in such a cold region is the exothermicity of grain-surface reactions. HN{sup 13}C reveals that the IRDC is actually composed of two distinct substructures ({sup s}ubclouds{sup )} separated in velocity space by {approx}1.4 km s{sup -1}. The narrow SiO component arises where the subclouds overlap. The spatial distribution of C{sub 2}H resembles that of NH{sub 2}D, which suggests that C{sub 2}H also traces cold gas in this IRDC.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States)
  2. Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520 (United States)
  3. European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany)
  4. Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 (United States)
  5. Caltech, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22131002
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 773; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; COLLISIONS; COSMIC DUST; EMISSION; GALAXIES; INFRARED RADIATION; LINE WIDTHS; METHANOL; NONLUMINOUS MATTER; SILICON OXIDES; SPATIAL DISTRIBUTION; TEMPERATURE RANGE 0065-0273 K; VELOCITY