ALCHEMI, an ALMA Comprehensive High-resolution Extragalactic Molecular Inventory
Astronomy and Astrophysics, vol. 656, pp. A46
Abstract
Context. The interstellar medium is the locus of physical processes affecting the evolution of galaxies which drive or are the result of star formation activity, supermassive black hole growth, and feedback. The resulting physical conditions determine the observable chemical abundances that can be explored through molecular emission observations at millimeter and submillimeter wavelengths. Aims. Our goal is to unveiling the molecular richness of the central region of the prototypical nearby starburst galaxy NGC 253 at an unprecedented combination of sensitivity, spatial resolution, and frequency coverage. Methods. We used the Atacama Large Millimeter/submillimeter Array (ALMA), covering a nearly contiguous 289 GHz frequency range between 84.2 and 373.2 GHz, to image the continuum and spectral line emission at 1.6″(∼28 pc) resolution down to a sensitivity of 30 − 50 mK. This article describes the ALMA Comprehensive High-resolution Extragalactic Molecular Inventory (ALCHEMI) large program. We focus on the analysis of the spectra extracted from the 15″ (∼255 pc) resolution ALMA Compact Array data. Results. We modeled the molecular emission assuming local thermodynamic equilibrium with 78 species being detected. Additionally, multiple hydrogen and helium recombination lines are identified. Spectral lines contribute 5 to 36% of the total emission in frequency bins of 50 GHz. We report the first extragalactic detections of C 2 H 5 OH, HOCN, HC 3 HO, and several rare isotopologues. Isotopic ratios of carbon, oxygen, sulfur, nitrogen, and silicon were measured with multiple species. Concluison. Infrared pumped vibrationaly excited HCN, HNC, and HC 3 N emission, originating in massive star formation locations, is clearly detected at low resolution, while we do not detect it for HCO + . We suggest high temperature conditions in these regions driving a seemingly “carbon-rich” chemistry which may also explain the observed high abundance of organic species close to those in Galactic hot cores. The L vib / L IR ratio was used as a proxy to estimate a 3% contribution from the proto super star cluster to the global infrared emission. Measured isotopic ratios with high dipole moment species agree with those within the central kiloparsec of the Galaxy, while those derived from 13 C/ 18 O are a factor of five larger, confirming the existence of multiple interstellar medium components within NGC 253 with different degrees of nucleosynthesis enrichment. The ALCHEMI data set provides a unique template for studies of star-forming galaxies in the early Universe.
Authors 35
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Atacama Large Millimeter Submillimeter Array · European Southern Observatory
Affiliation as printed
European Southern Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile
Joint ALMA Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA
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Institute of Astronomy and Astrophysics, Academia Sinica · The Graduate University for Advanced Studies, SOKENDAI · National Astronomical Observatory of Japan
Affiliation as printed
Department of Astronomy, School of Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-1855, Japan
Institute of Astronomy and Astrophysics, Academia Sinica, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
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Chalmers University of Technology
Affiliation as printed
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
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Institute of Astronomy and Astrophysics, Academia Sinica
Affiliation as printed
Institute of Astronomy and Astrophysics, Academia Sinica, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan
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Chalmers University of Technology
Affiliation as printed
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
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Max Planck Institute for Radio Astronomy
Affiliation as printed
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
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Affiliation as printed
Department of Physics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223–8522, Japan
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Affiliation as printed
Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
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The Graduate University for Advanced Studies, SOKENDAI · National Astronomical Observatory of Japan
Affiliation as printed
Department of Astronomy, School of Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-1855, Japan
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
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Institute of Space Sciences · European Southern Observatory
Affiliation as printed
European Southern Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile
Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Magrans, 08193 Barcelona, Spain
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Affiliation as printed
Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
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Chalmers University of Technology
Affiliation as printed
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
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Affiliation as printed
Astronomy Department, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904–4325, USA
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Consejo Superior de Investigaciones Científicas · Arcetri Astrophysical Observatory · Centro de Astrobiología
Affiliation as printed
Centro de Astrobiología (CSIC-INTA), Ctra. de Torrejón a Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA
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University of Manchester · Instituto de Astrofísica de Andalucía
Affiliation as printed
Intituto de Astrofísica de Andalucia (CSIC), Glorieta de al Astronomia s/n, 18008 Granada, Spain
Jodrell Bank Centre for Astrophysics, Department of Physics & Astronomy, School of Natural Sciences, The University of Manchester, Manchester M13 9PL, UK
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain
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DTU Space · University College London · Technical University of Denmark
Affiliation as printed
Cosmic Dawn Center, DTU Space, Technical University of Denmark, Elektrovej 327, Kgs. Lyngby 2800, Denmark
Department of Physics and Astronomy, University College London, Gower Street, London WC1E6BT, UK
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King Abdulaziz University · Chinese Academy of Sciences · Xinjiang Astronomical Observatory · Max Planck Institute for Radio Astronomy
Affiliation as printed
Astron. Dept., Faculty of Science, King Abdulaziz University, PO Box 80203 Jeddah 21589, Saudi Arabia
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, PR China
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Leiden University · Leiden Observatory · University College London
Affiliation as printed
Department of Physics and Astronomy, University College London, Gower Street, London WC1E6BT, UK
Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
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Max Planck Institute for Radio Astronomy
Affiliation as printed
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
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Arcetri Astrophysical Observatory
Affiliation as printed
INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
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The Graduate University for Advanced Studies, SOKENDAI · National Astronomical Observatory of Japan
Affiliation as printed
Department of Astronomy, School of Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-1855, Japan
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
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Affiliation as printed
Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Chalmers University of Technology
Affiliation as printed
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
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New Mexico Institute of Mining and Technology · National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory, PO Box O, 1003 Lopezville Road, Socorro, NM 87801, USA
New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801, USA
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Affiliation as printed
Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
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National Astronomical Observatory of Japan · The University of Tokyo
Affiliation as printed
Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
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Arcetri Astrophysical Observatory
Affiliation as printed
INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
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Consejo Superior de Investigaciones Científicas · Arcetri Astrophysical Observatory · Centro de Astrobiología
Affiliation as printed
Centro de Astrobiología (CSIC-INTA), Ctra. de Torrejón a Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
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Affiliation as printed
Department of Physics, General Studies, College of Engineering, Nihon University, Tamura-machi, Koriyama, Fukushima 963-8642, Japan
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
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Leiden University · Leiden Observatory · University College London
Affiliation as printed
Department of Physics and Astronomy, University College London, Gower Street, London WC1E6BT, UK
Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
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Max Planck Institute for Radio Astronomy
Affiliation as printed
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
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