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

Journal Article · Tue Aug 20 04:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/773/2/123· OSTI ID:22131002

Sanhueza, Patricio; Jackson, James M. ^[1]; Foster, Jonathan B. ^[2]; Jimenez-Serra, Izaskun ^[3]; Dirienzo, William J. ^[4]; Pillai, Thushara ^[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)

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}) 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.

• OSTI ID: 22131002
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 773; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
COLLISIONS
COSMIC DUST
EMISSION
GALAXIES
INFRARED RADIATION
LINE WIDTHS
METHANOL
NONLUMINOUS MATTER
SILICON OXIDES
SPATIAL DISTRIBUTION
TEMPERATURE RANGE 0065-0273 K
VELOCITY