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Distinct Chemical Regions in the "Prestellar" Infrared Dark Cloud G028.23–00.19

Sanhueza, Patricio and Jackson, James M. and Foster, Jonathan B. and Jimenez-Serra, Izaskun and Dirienzo, William J. and Pillai, Thushara (2013) Distinct Chemical Regions in the "Prestellar" Infrared Dark Cloud G028.23–00.19. Astrophysical Journal, 773 (2). Art. No. 123. ISSN 0004-637X. doi:10.1088/0004-637X/773/2/123.

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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 (~1520 M_☉) quiescent, cold (12 K) clumps known (MM1). The low temperature, high NH2D abundance, narrow molecular line widths, and absence of embedded infrared sources (from 3.6 to 70 μm) indicate that the clump is likely prestellar. Strong SiO emission with broad line widths (6-9 km s^(–1)) and high abundances ((0.8-4) × 10^(–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 (~2 km s^(–1)) and low abundances (4.3 × 10^(–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_3OH emission throughout the whole IRDC and the first detection of extended narrow methanol emission (~2 km s^(–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^(13)C reveals that the IRDC is actually composed of two distinct substructures ("subclouds") separated in velocity space by ~1.4 km s^(–1). The narrow SiO component arises where the subclouds overlap. The spatial distribution of C2H resembles that of NH_2D, which suggests that C_2H also traces cold gas in this IRDC.

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URLURL TypeDescription Paper
Jackson, James M.0000-0002-3466-6164
Additional Information:© 2013 American Astronomical Society. Received 2013 February 13; accepted 2013 June 29; published 2013 August 1. P.S. gratefully acknowledges the instructors of the CARMA Summer School 2011, especially for their enthusiasm and dedication to the professors John Carpenter, Nikolaus Volgenau, Melvyn Wright, Dick Plambeck, and Marc Pound. P.S. thanks Andrés Guzmán for his careful reading of the paper. We also thank the anonymous referee for helpful comments that improved the paper. P.S. and J.M.J. acknowledge funding support from NSF grant No.AST-0808001 and AST-1211844. I.J.-S. acknowledges the financial support from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007–2013) under REA grant agreement number PIIF-GA-2011-301538. Support for CARMA construction was derived from the states of California, Illinois, and Maryland, the James S. McDonnell Foundation, the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the University of Chicago, the Associates of the California Institute of Technology, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities.
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European Union Seventh Framework Programme (FP7/2007-2013) REAPIIF-GA-2011-301538
Subject Keywords: astrochemistry; ISM: abundances; ISM: clouds; ISM: molecules; stars: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20130923-074339392
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Official Citation: Distinct Chemical Regions in the "Prestellar" Infrared Dark Cloud G028.23–00.19 Patricio Sanhueza et al. 2013 ApJ 773 123
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41458
Deposited By: Ruth Sustaita
Deposited On:23 Sep 2013 16:22
Last Modified:10 Nov 2021 04:30

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