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The chemical structure of young high-mass star-forming clumps: (II) parsec-scale CO depletion and deuterium fraction of HCO+

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Caselli,  P.
Center for Astrochemical Studies at MPE, MPI for Extraterrestrial Physics, Max Planck Society;

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Sipilä,  O.
Center for Astrochemical Studies at MPE, MPI for Extraterrestrial Physics, Max Planck Society;

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Citation

Feng, S., Li, D., Caselli, P., Du, F., Lin, Y., Sipilä, O., et al. (2020). The chemical structure of young high-mass star-forming clumps: (II) parsec-scale CO depletion and deuterium fraction of HCO+. The Astrophysical Journal, 901(2): 145. doi:10.3847/1538-4357/abada3.


Cite as: http://hdl.handle.net/21.11116/0000-0007-88ED-5
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 n H ~ 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.