ALMA Observations of the IRDC Clump G34.43+00.24 MM3: DNC/HNC Ratio

Abstract

We have observed the clump G34.43+00.24 MM3 associated with an infrared dark cloud in DNC $J$=3--2, HN${}^{13}$C $J$=3--2, and N${}_2$H${}^{+}$ $J$=3--2 with the Atacama Large Millimeter/submillimeter Array (ALMA). The N${}_2$H${}^{+}$ emission is found to be relatively weak near the hot core and the outflows, and its distribution is clearly anti-correlated with the CS emission. This result indicates that a young outflow is interacting with cold ambient gas. The HN${}^{13}$C emission is compact and mostly emanates from the hot core, whereas the DNC emission is extended around the hot core. Thus, the DNC and HN${}^{13}$C emission traces warm regions near the protostar differently. The DNC emission is stronger than the HN${}^{13}$C emission toward most parts of this clump. The DNC/HNC abundance ratio averaged within a $15^{\prime \prime }\times 15^{\prime \prime }$ area around the phase center is higher than 0.06. This ratio is much higher than the value obtained by the previous single-dish observations of DNC and HN${}^{13}$C $J$=1--0 ($\sim$0.003). It seems likely that the DNC and HNC emission observed with the single-dish telescope traces lower density envelopes, while that observed with ALMA traces higher density and highly deuterated regions. We have compared the observational results with chemical-model results in order to investigate the behavior of DNC and HNC in the dense cores. Taking these results into account, we suggest that the low DNC/HNC ratio in the high-mass sources obtained by the single-dish observations are at least partly due to the low filling factor of the high density regions.

accepted to ApJ

References in corpus (9)

• Cold Dark Clouds: The Initial Conditions for Star Formation
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• The importance of the ortho:para H2 ratio for the deuteration of molecules during pre-protostellar collapse
• Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores
• A Molecular Line Observation toward Massive Clumps Associated with Infrared Dark Clouds
• Molecular Outflows and a Mid-Infrared Census of the Massive Star-Formation Region Associated with IRAS 18507+0121
• Distributed Low-Mass Star Formation in the IRDC G34.43+00.24
• Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data
• ALMA Observations of the IRDC Clump G34.43+00.24 MM3: 278 GHz Class I Methanol Masers

Cited by in corpus (8)

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• The ALMA Survey of 70 $\mu$m Dark High-mass Clumps in Early Stages (ASHES). V. Deuterated Molecules in the 70 $\mu$m dark IRDC G14.492-00.139
• Molecular Cloud Cores with High Deuterium Fraction: Nobeyama Single-Pointing Survey
• Molecular Cloud Cores with High Deuterium Fractions: Nobeyama Mapping Survey
• Digging into the Interior of Hot Cores with ALMA (DIHCA). V. Deuterium Fractionation of Methanol
• Molecular deuterations in massive Starless Clump Candidates
• Deuterium fractionation of a distant cold dark cloud along the line of sight of W51