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Title: The Chemical Structure of Young High-mass Star-forming Clumps. II. Parsec-scale CO Depletion and Deuterium Fraction of HCO+
Authors: Feng, S.
Li, D.
Caselli, P.
Du, F.
Lin, Y.
Sipilä, O.
Beuther, H.
Sanhueza, P.
Tatematsu, K.
Liu, Y.
Zhang, Q.
Wang, Y.
Hogge, T.
Jiménez Serra, I.
Lu, X.
Liu, T.
Wang, K.
Zhang, Y.
Zahorecz, S.
Li, G.
Liu, H. B.
Yuan, J.
Keywords: Interstellar medium;Interstellar molecules;Star formation;Massive stars;Astrochemistry
Issue Date: 1-Oct-2020
Publisher: The Institute of Physics (IOP)
DOI: 10.3847/1538-4357/abada3
Citation: The Astrophysical Journal 901(2): 145(2020)
Abstract: The physical and chemical properties of cold and dense molecular clouds are key to understanding how stars form. Using the IRAM 30 m and NRO 45 m telescopes, we carried out a Multiwavelength line-Imaging survey of the 70 μm-dArk and bright clOuds (MIAO). At a linear resolution of 0.1–0.5 pc, this work presents a detailed study of parsec-scale CO depletion and HCO+ deuterium (D-) fractionation toward four sources (G11.38+0.81, G15.22–0.43, G14.49–0.13, and G34.74–0.12) included in our full sample. In each source with T < 20 K and nH ~ 104–105 cm−3, we compared pairs of neighboring 70 μm bright and dark clumps and found that (1) the H2 column density and dust temperature of each source show strong spatial anticorrelation; (2) the spatial distribution of CO isotopologue lines and dense gas tracers, such as 1–0 lines of H13CO+ and DCO+, are anticorrelated; (3) the abundance ratio between C18O and DCO+ shows a strong correlation with the source temperature; (4) both the C18O depletion factor and D-fraction of HCO+ show a robust decrease from younger clumps to more evolved clumps by a factor of more than 3; and (5) preliminary chemical modeling indicates that chemical ages of our sources are ~8 × 104 yr, which is comparable to their free-fall timescales and smaller than their contraction timescales, indicating that our sources are likely dynamically and chemically young.
E-ISSN: 1538-4357
ISSN: 0004-637X
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