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Relationship between CH₃OD Abundance and Temperature in the Orion KL Nebula

Wilkins, Olivia H. and Blake, Geoffrey A. (2022) Relationship between CH₃OD Abundance and Temperature in the Orion KL Nebula. Journal of Physical Chemistry A, 126 (37). pp. 6473-6482. ISSN 1089-5639. PMCID PMC9514801. doi:10.1021/acs.jpca.2c01309.

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The relative abundances of singly deuterated methanol isotopologues, [CH2DOH]/[CH3OD], in star-formingregions deviate from the statistically expected ratio of 3. In Orion KL, the nearest high-mass star-forming region to Earth, the singly deuterated methanol ratio is about 1, and the cause for this observation has been explored through theory for nearly three decades. We present high-angular resolution observations of Orion KL using the Atacama Large Millimeter/submillimeter Array to map small-scale changes in CHOD column density across the nebula, which provide a new avenue to examine the deuterium chemistry during star and planet formation. By considering how CH₃OD column densities vary with temperature, we find evidence of chemical processes that can significantly alter the observed gasphase column densities. The astronomical data are compared with existing theoretical work and support D−H exchange between CH3OH and heavy water (i.e., HDO and D2O) at methanol’s hydroxyl site in the icy mantles of dust grains. The enhanced CH₃OD column densities are localized to the Hot Core-SW region, a pattern that may be linked to the coupled evolution of ice mantle chemistry and star formation in giant molecular clouds. This work provides new perspectives on deuterated methanol chemistry in Orion KL and informs considerations that may guide future theoretical, experimental, and observational work.

Item Type:Article
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URLURL TypeDescription CentralArticle
Wilkins, Olivia H.0000-0001-7794-7639
Blake, Geoffrey A.0000-0003-0787-1610
Alternate Title:Relationship between CH3OD Abundance and Temperature in the Orion KL Nebula
Additional Information:This work makes use of the following ALMA data: ADS/JAO.ALMA#2017.1.01149 and ADS/JAO.ALMA#2013.1.01034. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Tawain), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation (NSF) operated under Associated Universities, Inc. (AUI). This research made use of APLpy, an open-source plotting package for Python, (60) and the KInetic Database for Astrochemistry (KIDA), an online database of kinetic data. (57) This work was supported by the NSF Graduate Research Fellowship Program under Grant DGE-1144469 and NRAO Student Observing Support under Award SOSPA6-014. O.H.W. was additionally supported by an ARCS Los Angeles Founder Chapter scholarship. G.A.B. gratefully acknowledges support from the NSF AAG (AST-1514918) and NASA Astrobiology (NNX15AT33A) and Exoplanet Research (XRP, NNX16AB48G) programs. This work benefited from discussions with Brandon Carroll, Dana Anderson, Aida Behmard, Cam Buzard, Steve Charnley, and Catherine Walsh. Many thanks to the anonymous referees for their thoughtful comments and help in improving the manuscript. O.H.W. thanks Erica Keller, Sarah Wood, and the NRAO North American ALMA Science Center (NAASC) for their assistance with the data reduction.
Group:Division of Geological and Planetary Sciences
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
National Radio Astronomy ObservatorySOSPA6-014
Achievement Rewards for College Scientists Foundation (ARCS)UNSPECIFIED
Issue or Number:37
PubMed Central ID:PMC9514801
Record Number:CaltechAUTHORS:20220909-232915000
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116886
Deposited By: Olivia Warschaw
Deposited On:11 Sep 2022 19:40
Last Modified:27 Jan 2023 20:21

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