Low levels of methanol deuteration in the high-mass star-forming region NGC 6334I

Abstract

The abundance of deuterated molecules in a star-forming region is sensitive to the environment in which they are formed. Deuteration fractions therefore provide a powerful tool for studying the physical and chemical evolution of a star-forming system. While local low-mass star-forming regions show very high deuteration ratios, much lower fractions are observed towards Orion and the Galactic Centre. We derive methanol deuteration fractions at a number of locations towards the high-mass star-forming region NGC 6334I, located at a mean distance of 1.3 kpc, and discuss how these can shed light on the conditions prevailing during its formation. We use high sensitivity, high spatial and spectral resolution observations obtained with ALMA to study transitions of the less abundant, optically thin, methanol-isotopologues: (13)CH3OH, CH3(18)OH, CH2DOH and CH3OD, detected towards NGC 6334I. Assuming LTE and excitation temperatures of 120-330 K, we derive column densities for each of the species and use these to infer CH2DOH/CH3OH and CH3OD/CH3OH fractions. Interestingly, the column densities of CH3OD are consistently higher than those of CH2DOH throughout the region. All regions studied in this work show CH2DOH/CH3OH as well as CH2DOH/CH3OD ratios that are considerably lower than those derived towards low-mass star-forming regions and slightly lower than those derived for the high-mass star-forming regions in Orion and the Galactic Centre. The low ratios indicate a grain surface temperature during formation ~30 K, for which the efficiency of the formation of deuterated species is significantly reduced.

arXiv commentAccepted for publication in Astronomy & Astrophysics

References in corpus (24)

• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• First detection of triply-deuterated methanol
• Detection of doubly-deuterated methanol in the solar-type protostar IRAS16293-2422
• Exploring Molecular Complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)
• An extraordinary outburst in the massive protostellar system NGC6334I-MM1: quadrupling of the millimeter continuum
• Testing grain surface chemistry : a survey of deuterated formaldehyde and methanol in low-mass Class 0 protostars
• From Prestellar to Protostellar Cores II. Time Dependence and Deuterium Fractionation
• Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores
• Deuterated methanol in the pre-stellar core L1544
• Atomic Deuterium/Hydrogen in the Galaxy
• {Millimeter Multiplicity in NGC 6334 I and I(N)
• H-D Substitution in Interstellar Solid Methanol: A Key Route for D Enrichment
• Formaldehyde and methanol deuteration in protostars: fossiles from a past fast high density pre-collapse phase
• Water ice deuteration: a tracer of the chemical history of protostars
• ALMA Detection of Interstellar Methoxymethanol (CH${}_3$OCH${}_2$OH)
• Molecular line survey of the high-mass star-forming region NGC 6334I with Herschel/HIFI and the SMA
• Deuterated methanol in Orion BN/KL
• Deuterated molecules in Orion KL from Herschel/HIFI
• The Massive Protostellar Cluster NGC6334I at 220 AU Resolution: Discovery of Further Multiplicity, Diversity and a Hot Multi-Core
• Deuterated methanol on Solar System scale around the HH212 protostar
• The high velocity outflow in NGC6334I
• Hydrogen isotope exchanges between water and methanol in interstellar ices
• APEX CO (9-8) Mapping of an Extremely High-Velocity and Jet-like Outflow in a High-Mass Star-Forming Region

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• Astrochemistry During the Formation of Stars
• Complex organic molecules in low-mass protostars on solar system scales -- I. Oxygen-bearing species
• The complex chemistry of hot cores in Sagittarius B2(N): Influence of cosmic-ray ionization and thermal history
• The family of amide molecules toward NGC 6334I
• The GUAPOS project II. A comprehensive study of peptide-like bond molecules
• Methylamine and other simple N-bearing species in the hot cores NGC 6334I MM1-3
• Prestellar grain-surface origins of deuterated methanol in comet 67P/Churyumov-Gerasimenko
• N-bearing complex organics toward high-mass protostars: Constant ratios pointing to formation in similar pre-stellar conditions across a large mass range
• Interferometric observations of warm deuterated methanol in the inner regions of low-mass protostars
• Interstellar Glycolaldehyde, Methyl Formate, and Acetic Acid I: A Bi-modal Abundance Pattern in Star Forming Regions
• First Results of an ALMA Band 10 Spectral Line Survey of NGC 6334I: Detections of Glycolaldehyde (HC(O)CH${}_2$OH) and a New Compact Bipolar Outflow in HDO and CS
• The Extraordinary Outburst in the Massive Protostellar System NGC6334I-MM1: Strong Increase in Mid-Infrared Continuum Emission
• Importance of source structure on complex organics emission. I. Observations of CH${}_3$OH from low-mass to high-mass protostars
• Methanol deuteration in high-mass protostars
• Protostellar Interferometric Line Survey of the Cygnus X region (PILS-Cygnus) -- First results: observations of CygX-N30
• Importance of source structure on complex organics emission II. Can disks explain lack of methanol emission from some low-mass protostars?
• A Centimeter-wave Study of Methanol and Ammonia Isotopologues in Sgr B2(N): Physical and chemical differentiation between two hot cores
• On the ALMA observability of nascent massive multiple systems formed by gravitational instability
• Rotational and rovibrational spectroscopy of CD${}_3$OH with an account of CD${}_3$OH toward IRAS 16293$-$2422
• Importance of source structure on complex organics emission III. Effect of disks around massive protostars
• A deep search for large complex organic species toward IRAS16293-2422 B at 3 mm with ALMA
• ALMA Detection of Vibrationally Excited ($v{}_{\mathrm{t}}=1,2$) Acetic Acid toward NGC 6334I
• Deuterated methanol toward NGC 7538-IRS1
• On the Relationship between CH${}_3$OD Abundance and Temperature in the Orion KL Nebula
• Rotational spectroscopy of CH${}_3$OD with a reanalysis of CH${}_3$OD toward IRAS 16293$-$2422
• Digging into the Interior of Hot Cores with ALMA (DIHCA). V. Deuterium Fractionation of Methanol
• Gas phase Elemental abundances in Molecular cloudS (GEMS). IX. Deuterated compounds of H2S in starless cores
• Protostellar Interferometric Line Survey of the Cygnus-X region (PILS-Cygnus) -- The role of the external environment in setting the chemistry of protostars
• The ALMA-QUARKS survey: Extensive detection of acetamide in multiple high-mass star-forming regions
• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- X. Chemical differentiation among the massive cores in G9.62+0.19