The GUAPOS project: G31.41+0.31 Unbiased ALMA sPectral Observational Survey -- I. Isomers of C${}_2$H${}_4$O${}_2$

Abstract

Understanding the degree of chemical complexity that can be reached in star-forming regions, together with the identification of precursors of the building blocks of life in the interstellar medium, is one of the goals of astrochemistry. Unbiased spectral surveys with large bandwidth and high spectral resolution are thus needed, to resolve line blending in chemically rich sources and identify complex organic molecules. This kind of observations has been successfully carried out, mainly towards the Galactic Center, a region that shows peculiar environmental conditions. We present an unbiased spectral survey at 3mm of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this first paper, we present the survey and discuss the detection of the 3 isomers of C${}_2$H${}_4$O${}_2$: methyl formate, glycolaldehyde and acetic acid. Observations were carried out with ALMA and cover the entire Band 3 from 84 to 116 GHz with an angular resolution of $1.2^{{}^{\prime \prime }}$x$1.2^{{}^{\prime \prime }}$ and a spectral resolution of $\sim 0.488$ MHz. The transitions of the 3 molecules have been analyzed with the software XCLASS. All three isomers were detected and methyl formate and acetic acid abundances in G31 are the highest detected up to now, if compared to sources in literature. The size of the emission varies among the three isomers with acetic acid showing the most compact emission while methyl formate the most extended. The comparison with chemical models suggests the necessity of grain-surface routes for the formation of methyl formate in G31, while for glycolaldehyde both scenarios could be feasible. Proposed grain-surface reaction for acetic acid is not able to reproduce the observed abundance in this work, while gas-phase scenario should be further tested due to large uncertainties.

49 pages, 29 figures, accepted for publication in A&A

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Cited by in corpus (23)

• The GUAPOS project II. A comprehensive study of peptide-like bond molecules
• First detection of C${}_2$H${}_5$NCO in the ISM and search of other isocyanates towards the G+0.693-0.027 molecular cloud
• CoCCoA: Complex Chemistry in hot Cores with ALMA. Selected oxygen-bearing species
• The trans/cis ratio of formic, HCOOH, and thioformic, HC(O)SH, acids in the Interstellar Medium
• First detection in space of the high-energy isomer of cyanomethanimine: H2CNCN
• JOYS+: link between ice and gas of complex organic molecules. Comparing JWST and ALMA data of two low-mass protostars
• Fragmentation in the massive G31.41+0.31 protocluster
• Cloud-cloud collision as origin of the G31.41+0.31 massive protocluster
• Identification of the simplest sugar-like molecule glycolaldehyde towards the hot molecular core G358.93-0.03 MM1
• First survey of HCNH${}^{+}$ in high-mass star-forming cloud cores
• Reexploring Molecular Complexity with ALMA: Insights into chemical differentiation from the molecular composition of hot cores in Sgr B2(N2)
• Conformational isomerism of methyl formate: new detections of the higher-energy trans conformer and theoretical insights
• Complex organic molecules uncover deeply embedded precursors of hot cores
• Probing the kinematics and chemistry of the hot core Mon R 2 IRS 3 using ALMA observations
• Determination of the branching ratio of CH${}_3$OH + OH reaction on water ice surface at 10 K
• The GUAPOS project. VI: the chemical inventory of shocked gas
• A multi-scale view of the magnetic field morphology in the hot molecular core G31.41+0.31
• Expanding the C${}_3$H${}_6$O${}_2$ Isomeric Interstellar Inventory: Discovery of Lactaldehyde and Methoxyacetaldehyde in G+0.693-0.027
• Identification of molecular line emission using Convolutional Neural Networks
• Precursors of the RNA-world in space: Detection of ($Z$)-1,2-ethenediol in the interstellar medium, a key intermediate in sugar formation
• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- X. Chemical differentiation among the massive cores in G9.62+0.19
• The GUAPOS project -- VII: Physical structure and molecular environment of the G31.41+0.31 HII region
• Chemistry of Dark Molecular Clouds