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arXiv · 2111.13325

The ALMA Survey of 70 $μ$m Dark High-mass Clumps in Early Stages (ASHES). V. Deuterated Molecules in the 70 $μ$m dark IRDC G14.492-00.139

Takeshi Sakai·Patricio Sanhueza·Kenji Furuya·Ken'ichi Tatematsu·Shanghuo Li·Yuri Aikawa·Xing Lu·Qizhou Zhang·Kaho Morii·Fumitaka Nakamura·Hideaki Takemura·Natsuko Izumi·Tomoya Hirota·Andrea Silva·Andrés E. Guzmán·Nami Sakai·Satoshi Yamamoto
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Abstract

We have observed the 70 $μ$m dark infrared dark cloud (IRDC) G14.492-00.139 in the N$_2$D$^+$ $J$=3--2, DCO$^+$ $J$=3--2, DCN $J$=3--2, and C$^{18}$O $J$=2--1 lines, using the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the ALMA Survey of 70 $μ$m Dark High-mass Clumps in Early Stages (ASHES). We find that the spatial distribution is different among the observed emission from the deuterated molecular lines. The N$_2$D$^+$ emission traces relatively quiescent regions, while both the DCO$^+$ and DCN emission emanates mainly from regions with signs of active star-formation. In addition, the DCO$^+$/N$_2$D$^+$ ratio is found to be lower in several dense cores than in starless cores embedded in low-mass star-forming regions. By comparing the observational results with chemical model calculations, we discuss the origin of the low DCO$^+$/N$_2$D$^+$ ratio in this IRDC clump. The low DCO$^+$/N$_2$D$^+$ ratio can be explained if the temperature of the dense cores is in the range between the sublimation temperature of N$_2$ ($\sim$20 K) and CO ($\sim$25 K). The results suggest that the dense cores in G14.492-00.139 are warmer and denser than the dense cores in low-mass star-forming regions.

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Takeshi Sakai, Patricio Sanhueza, Kenji Furuya, Ken'ichi Tatematsu, Shanghuo Li, Yuri Aikawa, Xing Lu, Qizhou Zhang, Kaho Morii, Fumitaka Nakamura, Hideaki Takemura, Natsuko Izumi, Tomoya Hirota, Andrea Silva, Andrés E. Guzmán, Nami Sakai, Satoshi Yamamoto. 2021-11-26. The ALMA Survey of 70 $μ$m Dark High-mass Clumps in Early Stages (ASHES). V. Deuterated Molecules in the 70 $μ$m dark IRDC G14.492-00.139. https://doi.org/10.3847/1538-4357%2Fac3d2e

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