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CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow

Burkhardt, Andrew M. and Dollhopf, Niklaus M. and Corby, Joanna F. and Carroll, P. Brandon and Shingledecker, Christopher N. and Loomis, Ryan A. and Booth, Shawn Thomas and Blake, Geoffrey A. and Herbst, Eric and Remijan, Anthony J. and McGuire, Brett A. (2016) CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow. Astrophysical Journal, 827 (1). Art. No. 21. ISSN 0004-637X.

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L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a bipolar outflow, is an excellent source for studying shock chemistry, including grain-surface chemistry prior to shocks, and post-shock, gas-phase processing. The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000 years ago, respectively. Prior to these shock events, temperatures were too low for most complex organic molecules to undergo thermal desorption. Thus, the shocks should have liberated these molecules from the ice grain-surfaces en masse, evidenced by prior observations of SiO and multiple grain mantle species commonly associated with shocks. Grain species, such as OCS, CH_3OH, and HNCO, all peak at different positions relative to species that are preferably formed in higher-velocity shocks or repeatedly shocked material, such as SiO and HCN. Here, we present high spatial resolution (~3") maps of CH_3OH, HNCO, HCN, and HCO^+ in the southern portion of the outflow containing B1 and B2, as observed with Combined Array for Research in Millimeter-Wave Astronomy. The HNCO maps are the first interferometric observations of this species in L1157. The maps show distinct differences in the chemistry within the various shocked regions in L1157B. This is further supported through constraints of the molecular abundances using the non-LTE code radex. We find that the east/west chemical differentiation in C2 may be explained by the contrast of the shock's interaction with either cold, pristine material or warm, previously shocked gas, as seen in enhanced HCN abundances. In addition, the enhancement of the HNCO abundance toward the the older shock, B2, suggests the importance of high-temperature O-chemistry in shocked regions.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Burkhardt, Andrew M.0000-0003-0799-0927
Carroll, P. Brandon0000-0002-3191-5401
Shingledecker, Christopher N.0000-0002-5171-7568
Loomis, Ryan A.0000-0002-8932-1219
Blake, Geoffrey A.0000-0003-0787-1610
Remijan, Anthony J.0000-0001-9479-9287
McGuire, Brett A.0000-0003-1254-4817
Additional Information:© 2016 American Astronomical Society. Received 2016 February 4; revised 2016 May 26; accepted 2016 May 26; published 2016 August 3. E.H., A.M.B, and C.N.S. thank the National Science Foundation (NSF) for continuing to support the astrochemistry program at the University of Virginia and the NASA Exobiology and Evolutionary Biology Program through a subcontract from Rensselaer Polytechnic Institute. N.M.D. gratefully acknowledges funding by the National Radio Astronomy Observatory Summer Research Internship, a Research Experience for Undergraduates funded by the NSF and Peter Teuben for helpful discussion. B.A.M. gratefully acknowledges funding by an NSF Graduate Research Fellowship during initial portions of this work. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Portions of this material are based upon work at the Caltech Submillimeter Observatory, which was operated by the California Institute of Technology under cooperative agreement with the National Science Foundation (AST-0838261). Support for CARMA construction was derived from the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the James S. McDonnell Foundation, the Associates of the California Institute of Technology, the University of Chicago, the states of California, Illinois, and Maryland, and the National Science Foundation. CARMA development and operations were supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities.
Funding AgencyGrant Number
National Radio Astronomy ObservatoryUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Kenneth T. and Eileen L. Norris FoundationUNSPECIFIED
James S. McDonnell FoundationUNSPECIFIED
Caltech AssociatesUNSPECIFIED
University of ChicagoUNSPECIFIED
states of California, Illinois, and MarylandUNSPECIFIED
Subject Keywords:astrochemistry; ISM: individual objects (L1157) ; ISM: molecules
Issue or Number:1
Record Number:CaltechAUTHORS:20160805-095356318
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Official Citation:Andrew M. Burkhardt et al 2016 ApJ 827 21
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69468
Deposited By: Ruth Sustaita
Deposited On:05 Aug 2016 17:38
Last Modified:09 Mar 2020 13:19

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