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The Deuterium Fraction in Massive Starless Cores and Dynamical Implications

Kong, Shuo and Tan, Jonathan C. and Caselli, Paola and Fontani, Francesco and Pillai, Thushara and Butler, Michael J. and Shimajiri, Yoshito and Nakamura, Fumitaka and Sakai, Takeshi (2016) The Deuterium Fraction in Massive Starless Cores and Dynamical Implications. Astrophysical Journal, 821 (2). Art. No. 94. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20160623-100705268

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Abstract

We study deuterium fractionation in two massive starless/early-stage cores, C1-N and C1-S, in Infrared Dark Cloud G028.37+00.07, which was first identified by Tan et al. with ALMA. Line emission from multiple transitions of N_2H^+ and N_2D^+ were observed with the ALMA, CARMA, SMA, JCMT, NRO 45 m, and IRAM 30 m telescopes. By simultaneously fitting the spectra, we estimate the excitation conditions and deuterium fraction, D_(frac)^N_2H^+ ≡ [N_2D^+] [N_2H^+], with values of D_(frac)^N_2H^+ ≃ 0.2–0.7, several orders of magnitude above the cosmic [D]/[H] ratio. Additional observations of o-H_2D^+ are also presented that help constrain the ortho-to-para ratio of H_2, which is a key quantity affecting the degree of deuteration. We then present chemodynamical modeling of the two cores, especially exploring the implications for the collapse rate relative to free-fall, αff. In order to reach the high level of observed deuteration of N_2H^+, we find that the most likely evolutionary history of the cores involves collapse at a relatively slow rate, ≾ one-tenth of free-fall.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/0004-637X/821/2/94DOIArticle
http://iopscience.iop.org/article/10.3847/0004-637X/821/2/94PublisherArticle
http://arxiv.org/abs/1509.08684arXivDiscussion Paper
Additional Information:© 2016 The American Astronomical Society. Received 2015 September 29; accepted 2016 January 27; published 2016 April 15. We thank an anonymous referee for helpful comments. We thank Jan Wouterloot for helping with the JCMT observation. S.K. and J.C.T. acknowledge an NRAO/SOS grant and NSF grant AST 1411527. P.C. acknowledges the financial support of the European Research Council (ERC; project PALs 320620). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00236.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. 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 (NSF AST 08-38226) and by the CARMA partner universities. The James Clerk Maxwell Telescope has historically been operated by the Joint Astronomy Center on behalf of the Science and Technology Facilities Council of the United Kingdom, the National Research Council of Canada and the Netherlands Organization for Scientific Research. We are grateful to the staff members at the Nobeyama Radio Observatory (NRO) for both operating the 45 m and helping us with the data reduction; NRO is a branch of the National Astronomical Observatory, National Institutes of Natural Sciences, Japan. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Facilities: ALMA - Atacama Large Millimeter Array, CARMA - Combined Array for Research in Millimeter-Wave Astronomy, SMA - SubMillimeter Array, JCMT - James Clerk Maxwell Telescope, No:45m - , IRAM:30m - .
Funders:
Funding AgencyGrant Number
NSFAST 1411527
European Research Council (ERC)320620
states of California, Illinois, and MarylandUNSPECIFIED
James S. McDonnell FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Kenneth T. and Eileen L. Norris FoundationUNSPECIFIED
University of ChicagoUNSPECIFIED
Caltech AssociatesUNSPECIFIED
NSFAST 08-38226
National Radio Astronomy ObservatoryUNSPECIFIED
CARMA partner universitiesUNSPECIFIED
Subject Keywords:evolution; ISM: clouds; ISM: magnetic fields; ISM: structure; stars: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20160623-100705268
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160623-100705268
Official Citation:Shuo Kong et al 2016 ApJ 821 94
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:68630
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:23 Jun 2016 22:10
Last Modified:03 Oct 2019 10:15

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