ALMAGAL
Astronomy and Astrophysics, vol. 711, pp. A118
Abstract
Context . High-mass star-forming regions are rich in complex organic molecules (COMs), which are carbon-bearing species with at least six atoms. Their formation pathways remain debated. The ALMA evolutionary study of high-mass protocluster formation in the GALaxy (ALMAGAL) survey provides a unique opportunity to probe this chemical complexity in a large statistical significant sample of high-mass star-forming regions. Aims . We present a detailed molecular line analysis of one of the most chemically rich cores in the ALMAGAL sample, the high-mass core 9 in the AG318.9477−00.1960 clump (AG318−c9), located at a heliocentric distance of ∼10.4 kpc. This source was selected because it combines an exceptionally high line density with a relatively simple kinematic structure, making it an optimal template for chemical analysis in the survey. We further assessed whether the emission of selected COMs, that is, ethylene glycol ((CH 2 OH) 2 ; EG), glycolaldehyde (CH 2 (OH)CHO; GA), and methyl formate (CH 3 OCHO; MF), can be used to trace the innermost regions of hot molecular cores (HMCs). Methods . We analysed ALMA Band 6 observations (∼217–221 GHz). Spectral line identification and local thermodynamic equilibrium modelling were performed using the software called MAdrid Data CUBe Analysis (MADCUBA). We derived the physical parameters, including the column density ( N ), excitation temperature ( T ex ), velocity, line width, and molecular abundances relative to H 2 , for all detected species. The chemical inventory of AG318−c9 was compared with that of the HMC G31.41 + 0.31 (G31). In addition, we performed a pixel-by-pixel analysis of EG, GA, and MF to generate spatially resolved N and T ex maps and corresponding radial profiles. Results . We report the detection of 65 molecular species, including 31 main species and 34 isotopologues and vibrationally excited species. Of these, 44 are O-bearing species, 28 are N-bearing, 8 are S-bearing, and 2 are Si-bearing. While AG318−c9 exhibits lower abundances than G31 overall, it shows detections of species that have not yet been reported in G31, such as ethyl formate (C 2 H 5 OCHO). Moreover, 12 species depart from the general trend, displaying relative overabundances in AG318−c9. The comparison also reveals a chemical differentiation between O- and N- bearing COMs, with O-bearing species systematically more abundant in G31. Regarding EG, GA, and MF, the latter is the most abundant ( X ∼ 3 × 10 −8 ), followed by EG ( X ∼ 7 × 10 −9 ) and GA ( X ∼ 2 × 10 −9 ). The N and T ex maps suggest that MF is the most spatially extended species, whereas EG and GA are more compact and confined to the innermost hot region. Conclusions . AG318−c9 reveals a rich chemical inventory characteristic of an HMC. The chemical comparison with G31 suggests that AG318−c9 is a less evolved hot core dominated by the recent sublimation of ice mantles, in contrast to the higher abundances observed in the possible more evolved G31. MF emerges as an excellent tracer of the gas temperature in HMCs owing to its wide spatial extent and wide dynamic range of the excitation temperature. In contrast, EG and GA are more compact and preferentially trace the innermost high-density regions of the core, suggesting a high sublimation temperature threshold and supporting a shared grain-surface formation pathway. While EG and MF seem to be partly limited by sensitivity, GA reflects an intrinsically central distribution.
Authors 39
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Arcetri Astrophysical Observatory · University of Florence · National Institute for Astrophysics
Affiliation as printed
INAF-Osservatorio Astrofisico di Arcetri
Università degli Studi di Firenze
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF-Osservatorio Astrofisico di Arcetri
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Consejo Superior de Investigaciones Científicas · Centro de Astrobiología
Affiliation as printed
Centro de Astrobiología (CAB), CSIC-INTA
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Consejo Superior de Investigaciones Científicas · Centro de Astrobiología
Affiliation as printed
Centro de Astrobiología (CAB), CSIC-INTA
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF-Osservatorio Astrofisico di Arcetri
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Institute of Space Sciences · Consejo Superior de Investigaciones Científicas · Institut d'Estudis Espacials de Catalunya
Affiliation as printed
Institut de Ciències de l’Espai (ICE), CSIC
Institut d’Estudis Espacials de Catalunya (IEEC)
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Affiliation as printed
University of Connecticut, Department of Physics
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
INAF-Istituto di Astrofisica e Planetologia Spaziale
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Max Planck Institute for Astronomy
Affiliation as printed
Max Planck Institute for Astronomy
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory
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Affiliation as printed
Departamento de Astronomía, Universidad de Chile
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National Cheng Kung University
Affiliation as printed
Department of Physics, National Cheng Kung University
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Consejo Superior de Investigaciones Científicas · Centro de Astrobiología
Affiliation as printed
Centro de Astrobiología (CAB), CSIC-INTA
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
INAF-Istituto di Astrofisica e Planetologia Spaziale
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF-Osservatorio Astrofisico di Arcetri
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Affiliation as printed
I. Physikalisches Institut, Universität zu Köln
Jodrell Bank Centre for Astrophysics
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory
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Institute of Astronomy and Astrophysics, Academia Sinica · East Asian Observatory · Academia Sinica
Affiliation as printed
East Asian Observatory
Institute of Astronomy and Astrophysics, Academia Sinica
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Affiliation as printed
School of Engineering and Physical Sciences, Isaac Newton Building, University of Lincoln
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Affiliation as printed
I. Physikalisches Institut, Universität zu Köln
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Korea Astronomy and Space Science Institute · Korea University of Science and Technology
Affiliation as printed
Korea Astronomy and Space Science Institute
University of Science and Technology, Korea (UST)
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Royal Observatory · UK Astronomy Technology Centre
Affiliation as printed
UK Astronomy Technology Centre, Royal Observatory Edinburgh
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Affiliation as printed
Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen
Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik
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Affiliation as printed
Faculty of Physics, University of Duisburg-Essen
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Affiliation as printed
Jet Propulsion Laboratory, California Institute of Technology
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
INAF-Istituto di Astrofisica e Planetologia Spaziale
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
INAF-Istituto di Astrofisica e Planetologia Spaziale
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Affiliation as printed
I. Physikalisches Institut, Universität zu Köln
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF-Osservatorio Astrofisico di Arcetri
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University of Rome Tor Vergata · Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
Dipartimento di Fisica, Università di Roma Tor Vergata
INAF-Istituto di Astrofisica e Planetologia Spaziale
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
INAF-Istituto di Astrofisica e Planetologia Spaziale
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Affiliation as printed
I. Physikalisches Institut, Universität zu Köln
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
INAF-Istituto di Astrofisica e Planetologia Spaziale
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University of Groningen · Space Research Organisation Netherlands
Affiliation as printed
Kapteyn Astronomical Institute, University of Groningen
SRON Netherlands Institute for Space Research
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Institute of Astronomy and Astrophysics, Academia Sinica · Academia Sinica
Affiliation as printed
Institute of Astronomy and Astrophysics, Academia Sinica
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
Affiliation as printed
INAF-Istituto di Astrofisica e Planetologia Spaziale
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Affiliation as printed
Center for Data and Simulation Science, University of Cologne
I. Physikalisches Institut, Universität zu Köln
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Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian
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Affiliation as printed
I. Physikalisches Institut, Universität zu Köln
Research Center for Computational Earth and Space Science, Zhe-jiang Laboratory
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