Resolving desorption of complex organic molecules in a hot core: Transition from non-thermal to thermal desorption or two-step thermal desorption?

Abstract

Using the high angular resolution provided by the ALMA interferometre we want to resolve the COM emission in the hot molecular core Sagittarius B2(N1) and thereby shed light on the desorption process of Complex Organic Molecules (COMs) in hot cores. We use data taken as part of the 3 mm spectral line survey Re-exploring Molecular Complexity with ALMA (ReMoCA) to investigate the morphology of COM emission in Sagittarius B2(N1). Spectra of ten COMs are modelled under the assumption of LTE and population diagrams are derived for positions at various distances to the south and west from the continuum peak. Based on this analysis, resolved COM rotation temperature and COM abundance profiles are derived. Based on the morphology, a rough separation into O- and N-bearing COMs can be done. Temperature profiles are in agreement with expectations of protostellar heating of an envelope with optically thick dust. Abundance profiles reflect a similar trend as seen in the morphology and, to a great extent, agree with results of astrochemical models that, besides the co-desorption with water, predict that O-bearing COMs are mainly formed on dust grain surfaces at low temperatures while at least some N-bearing COMs and CH${}_3$CHO are substantially formed in the gas phase at higher temperatures. Our observational results, in comparison with model predictions, suggest that COMs that are exclusively or to a great extent formed on dust grains desorb thermally at ~100 K from the grain surface likely alongside water. Non-zero abundance values below ~100 K suggest that another desorption process is at work at these low temperatures: either non-thermal desorption or partial thermal desorption related to lower binding energies experienced by COMs in the outer, water-poor ice layers. In either case, this is the first time that the transition between two regimes of COM desorption has been resolved in a hot core.

Accepted for publication in A&A

References in corpus (25)

• Array Programming with NumPy
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Testing grain-surface chemistry in massive hot-core regions
• Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanide
• Binding energies: new values and impact on the efficiency of chemical desorption
• The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core
• Experimental evidence for Glycolaldehyde and Ethylene Glycol formation by surface hydrogenation of CO molecules under dense molecular cloud conditions
• Modeling Complex Organic Molecules in dense regions: Eley-Rideal and complex induced reaction
• Formation of Complex Organic Molecules in Cold Interstellar Environments through non-diffusive grain-surface and ice-mantle chemistry
• Seeds of Life in Space (SOLIS) III. Formamide in protostellar shocks: evidence for gas-phase formation
• A new modified-rate approach for gas-grain chemical simulations
• Thermal desorption of circumstellar and cometary ice analogs
• Chemical modelling of complex organic molecules with peptide-like bonds in star-forming regions
• Cloud-cloud collision as drivers of the chemical complexity in Galactic Centre molecular clouds
• Astrochemistry at work in the L1157-B1 shock: acetaldehyde formation
• The Physical and chemical structure of Sagittarius B2 -- IV. Converging filaments in the high-mass cluster forming region Sgr B2(N)
• The complex organic molecular content in the L1498 starless core
• Complex organic molecules in diffuse clouds along the line of sight to Sgr B2
• Far-infrared laboratory spectroscopy of aminoacetonitrile and first interstellar detection of its vibrationally excited transitions
• Methyl isocyanate CH3NCO: An important missing organic in current astrochemical networks
• The Role of Radiolysis in the Modelling of C${}_2$H${}_4$O${}_2$ Isomers and Dimethyl Ether in Cold Dark Clouds
• Deuterium fractionation as a multi-phase component tracer in the Galactic Centre
• New spectral characterization of dimethyl ether isotopologues CH${}_3$OCH${}_3$ and ${}^{13}$CH${}_3$OCH${}_3$ in the THz region

Cited by in corpus (14)

• ALMA-IMF XI: The sample of hot core candidates A rich population of young high-mass proto-stars unveiled by the emission of methyl formate
• Shocking Sgr B2(N1) with its own outflow: A new perspective on segregation between O- and N-bearing molecules
• Evidence for ubiquitous carbon grain destruction in hot protostellar envelopes
• A deep search for large complex organic species toward IRAS16293-2422 B at 3 mm with ALMA
• Reexploring Molecular Complexity with ALMA: Insights into chemical differentiation from the molecular composition of hot cores in Sgr B2(N2)
• Complex organic molecules uncover deeply embedded precursors of hot cores
• Planetesimal formation via the streaming instability in simulations of infall dominated young disks
• Identification of hot gas around low-mass protostars
• PRODIGE - envelope to disk with NOEMA: V. Low 12C/13C ratios for CH3OH and CH3CN in hot corinos
• Rotation-tunneling spectrum and astrochemical modeling of dimethylamine, CH${}_3$NHCH${}_3$, and searches for it in space
• The salty emission of the intermediate-mass AGB star OH 30.1 -0.7
• Correlations among complex organic molecules around protostars: Effects of physical structure
• Looking for evidence of high-mass star formation at core scale in a massive molecular clump
• One-dimensional and time-dependent modelling of complex organic molecules in protostars