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An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud. II. CCS and HC_7N Chemistry and Three Modes of Star Formation in the Filaments

Seo, Young Min and Majumdar, Liton and Goldsmith, Paul F. and Shirley, Yancy L. and Willacy, Karen and Ward-Thompson, Derek and Friesen, Rachel and Frayer, David T. and Church, Sarah E. and Chung, Dongwoo and Cleary, Kieran and Cunningham, Nichol and Devaraj, Kiruthika and Egan, Dennis and Gaier, Todd and Gawande, Rohit and Gundersen, Joshua O. and Harris, Andrew I. and Kangaslahti, Pekka and Readhead, Anthony C. S. and Samoska, Lorene and Sieth, Matthew and Stennes, Michael and Voll, Patricia and White, Steve (2019) An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud. II. CCS and HC_7N Chemistry and Three Modes of Star Formation in the Filaments. Astrophysical Journal, 871 (2). Art. No. 134. ISSN 1538-4357. http://resolver.caltech.edu/CaltechAUTHORS:20190130-121937125

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Abstract

We present deep CCS and HC_7N observations of the L1495-B218 filaments in the Taurus molecular cloud obtained using the K-band focal plane array on the 100 m Green Bank Telescope. We observed the L1495-B218 filaments in CCS J_N = 2_1–1_0 and HC_7N J = 21−20 with a spectral resolution of 0.038 km s^(−1) and an angular resolution of 31''. We observed strong CCS emission in both evolved and young regions and weak emission in two evolved regions. HC_7N emission is observed only in L1495A-N and L1521D. We find that CCS and HC_7N intensity peaks do not coincide with NH_3 or dust continuum intensity peaks. We also find that the fractional abundance of CCS does not show a clear correlation with the dynamical evolutionary stage of dense cores. Our findings and chemical modeling indicate that the fractional abundances of CCS and HC_7N are sensitive to the initial gas-phase C/O ratio, and they are good tracers of young condensed gas only when the initial C/O is close to solar value. Kinematic analysis using multiple lines, including NH_3, HC_7N, CCS, CO, HCN, and HCO^+, suggests that there may be three different star formation modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has formed a stellar cluster with large-scale inward flows (fast mode), whereas L1521D, a core embedded in a filament, is slowly contracting because of its self-gravity (slow mode). There is also one isolated core that appears to be marginally stable and may undergo quasi-static evolution (isolated mode).


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/aaf887DOIArticle
https://arxiv.org/abs/1812.06121arXivDiscussion Paper
ORCID:
AuthorORCID
Seo, Young Min0000-0003-2122-2617
Majumdar, Liton0000-0001-7031-8039
Goldsmith, Paul F.0000-0002-6622-8396
Willacy, Karen0000-0001-6124-5974
Ward-Thompson, Derek0000-0003-1140-2761
Friesen, Rachel0000-0001-7594-8128
Frayer, David T.0000-0003-1924-1122
Chung, Dongwoo0000-0003-2618-6504
Harris, Andrew I.0000-0001-6159-9174
Readhead, Anthony C. S.0000-0001-9152-961X
Alternate Title:An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud. II. CCS and HC7N Chemistry and Three Modes of Star Formation in the Filaments
Additional Information:© 2019. The American Astronomical Society. Received 2017 December 21; revised 2018 December 12; accepted 2018 December 13; published 2019 January 28. We thank the anonymous referee for providing constructive comments that have improved the contents of this article. This research was performed in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We thank Hugo Medrano for his contributions to Argus. Y.S. and Y.L.S. were partially supported by NSF grant No. AST-1410190. Y.S. and L.M. acknowledges support from the NASA postdoctoral program. Software: CLASS (Pety 2005), GBTIDL (Marganian et al. 2006), NAUTILUS (Ruaud et al. 2016).
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
NSFAST-1410190
NASA Postdoctoral ProgramUNSPECIFIED
Subject Keywords:ISM: clouds; ISM: molecules; radio lines: ISM; stars: formation; surveys
Record Number:CaltechAUTHORS:20190130-121937125
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190130-121937125
Official Citation:Young Min Seo et al 2019 ApJ 871 134
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92528
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:31 Jan 2019 00:05
Last Modified:31 Jan 2019 00:05

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