Digging into the Interior of Hot Cores with ALMA (DIHCA). V. Deuterium Fractionation of Methanol

Abstract

We have observed the ${}^{13}$CH${}_3$OH $5_1-4_1$ A${}^{+}$, ${}^{13}$CH${}_3$OH $14_1-13_2$ A${}^{-}$, and CH${}_2$DOH $8_{2,6}-8_{1,7}$ $e_0$ lines toward 24 high-mass star-forming regions by using Atacama Large Millimeter/submillimeter Array (ALMA) with an angular resolution of about 0${}^{\prime \prime }$.3. This resolution corresponds to a linear scale of 400-1600 au, allowing us to resolve individual cores properly. We detected the ${}^{13}$CH${}_3$OH and CH${}_2$DOH emission near the continuum peaks in many of these regions. From the two ${}^{13}$CH${}_3$OH lines, we calculated the temperature toward the ${}^{13}$CH${}_3$OH peaks, and confirm that the emission traces hot ($>$100 K) regions. The $N$(CH${}_2$DOH)/$N$(${}^{12}$CH${}_3$OH) ratio in the observed high-mass star-forming regions is found to be lower than that in low-mass star-forming regions. We have found no correlation between the $N$(CH${}_2$DOH)/$N$(${}^{13}$CH${}_3$OH) or $N$(CH${}_2$DOH)/$N$(${}^{12}$CH${}_3$OH) ratios and either temperatures or distance to the sources, and have also found a source-to-source variation in these ratios. Our model calculations predict that the $N$(CH${}_2$DOH)/$N$(${}^{12}$CH${}_3$OH) ratio in hot cores depends on the duration of the cold phase; the shorter the cold phase, the lower the deuterium fractionation in the hot cores. We have suggested that the lower $N$(CH${}_2$DOH)/$N$(${}^{12}$CH${}_3$OH) ratio in high-mass star-forming regions compared to that in low-mass star-forming regions is due to the shorter duration of the cold phase and that the diversity in the $N$(CH${}_2$DOH)/$N$(${}^{12}$CH${}_3$OH) ratio in high-mass star-forming regions is due to the diversity in the length of the cold prestellar phase, and not the time that the objects have been in the hot core phase.

arXiv commentAccepted for publication in ApJ (49 pages)

References in corpus (40)

• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• Massive molecular outflows
• ATLASGAL --- properties of a complete sample of Galactic clumps
• A Geometric Determination of the Distance to the Galactic Center
• Chemistry in Infrared Dark Cloud Clumps: a Molecular Line Survey at 3 mm
• The ALMA Survey of 70 $\mu$m dark High-mass clumps in Early Stages (ASHES). I. Pilot Survey: Clump Fragmentation
• Exploring Molecular Complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)
• The Physical and Chemical Structure of Hot Molecular Cores
• The N2D+/N2H+ ratio as an evolutionary tracer of Class 0 protostars
• Massive Protostars in the Infrared Dark Cloud MSXDC G034.43+00.24
• Gravity Driven Magnetic Field at ~1000 au Scales in High-mass Star Formation
• Formaldehyde and methanol deuteration in protostars: fossiles from a past fast high density pre-collapse phase
• Infall Signatures in a Prestellar Core embedded in the High-Mass 70 $\mu$m Dark IRDC G331.372-00.116
• Water deuteration and ortho-to-para nuclear spin ratio of H2 in molecular clouds formed via the accumulation of HI gas
• Deuteration and evolution in the massive star formation process: the role of surface chemistry
• HD depletion in starless cores
• The ALMA Survey of 70 $\mu$m Dark High-mass Clumps in Early Stages (ASHES). IX. Physical Properties and Spatial Distribution of Cores in IRDCs
• Molecular outflows within the filamentary infrared dark cloud G34.43+0.24
• A systematic TMRT observational study of Galactic ${}^{12}$C/${}^{13}$C ratios from Formaldehyde
• The Deuterium Fraction in Massive Starless Cores and Dynamical Implications
• Deuterated methanol in Orion BN/KL
• Low levels of methanol deuteration in the high-mass star-forming region NGC 6334I
• Magnetic Fields in Massive Star-Forming Regions (MagMaR) I. Linear Polarized Imaging of the UCHII Region G5.89-0.39
• Deuterium Fractionation as an Evolutionary Probe in the Infrared Dark Cloud G28.34+0.06
• Digging into the Interior of Hot Cores with ALMA (DIHCA). I. Dissecting the High-mass Star-Forming Core G335.579-0.292 MM1
• ALMA Observations of the IRDC Clump G34.43+00.24 MM3: Hot Core and Molecular Outflows
• Deuterium Fractionation as an Evolutionary Probe in Massive Proto-stellar/cluster Cores
• Digging into the Interior of Hot Cores with ALMA (DIHCA). III: The Chemical Link between NH${}_2$CHO, HNCO, and H${}_2$CO
• Methanol deuteration in high-mass protostars
• Protostellar Interferometric Line Survey of the Cygnus X region (PILS-Cygnus) -- First results: observations of CygX-N30
• 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
• Digging into the Interior of Hot Cores with ALMA (DIHCA). II. Exploring the Inner Binary (Multiple) System Embedded in G335 MM1 ALMA1
• Complex organic molecules detected in twelve high-mass star-forming regions with Atacama Large Millimeter/submillimeter Array (ALMA)
• Salt-bearing disk candidates around high-mass young stellar objects
• The Extremely High-Velocity Outflow from the Luminous Young Stellar Object G5.89-0.39
• ALMA Observations of the IRDC Clump G34.43+00.24 MM3: DNC/HNC Ratio
• G5.89: An Explosive Outflow Powered by a Proto-Stellar Merger?
• Structure, Dynamics and Deuterium Fractionation of Massive Pre-Stellar Cores
• Carbon Isotope Fractionation of Complex Organic Molecules in Star-Forming Cores
• Spectrometer Using superconductor MIxer Receiver (SUMIRE) for Laboratory Submillimeter Spectroscopy

Cited by in corpus (2)

• Digging into the Interior of Hot Cores with ALMA (DIHCA). VII. Disk candidates around high-mass stars and evidence of anisotropic infall
• Dense Molecular Clumps with Large Blue Asymmetries: Evidence for Collapse