FAUST
Astronomy and Astrophysics, vol. 695, pp. A78
Abstract
Context. Young low-mass protostars often possess hot corinos, which are compact, hot, and dense regions that are bright in interstellar complex organic molecules (iCOMs). In addition to their prebiotic role, iCOMs can be used as a powerful tool to characterize the chemical and physical properties of hot corinos. Aims. Using ALMA/FAUST data, our aim was to explore the iCOM emission at <50 au scale around the Class 0 prototypical hot corino IRAS 4A2. Methods. We imaged IRAS 4A2 in six abundant common iCOMs (CH 3 OH, HCOOCH 3 , CH 3 CHO, CH 3 CH 2 OH, CH 2 OHCHO, and NH 2 CHO), and derived their emitting sizes. The column density and gas temperature for each species were derived at 1σ from a multiline analysis by applying a non-LTE approach for CH 3 OH, and LTE population or rotational diagram analysis for the other iCOMs. Thanks to the unique estimates of the absorption from foreground millimeter dust toward IRAS 4A2, we derived for the first time unbiased gas temperatures and column densities. Results. We resolved the IRAS 4A2 hot corino, and found evidence for a chemical spatial distribution in the inner 50 au, with the outer emitting radius increasing from ∼22–23 au for NH 2 CHO and CH 2 OHCHO, followed by CH 3 CH 2 OH (∼27 au), CH 3 CHO (∼28 au), HCOOCH 3 (∼36 au), and out to ∼40 au for CH 3 OH. Combining our estimate of the gas temperature probed by each iCOM with their beam-deconvolved emission sizes, we inferred the gas temperature profile of the hot corino on scales of 20–50 au in radius, and found a power-law index q of approximately –1. Conclusions. We observed, for the first time, a chemical segregation in iCOMs of the IRAS 4A2 hot corino, and derived the gas temperature profile of its inner envelope. The derived profile is steeper than when considering a simple spherical collapsing and optically thin envelope, hinting at a partially optically thick envelope or a gravitationally unstable disk-like structure.
Authors 23
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European Southern Observatory · Stockholm University · AlbaNova · University of Bologna
Affiliation as printed
DIFA, Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
Department of Astronomy, Stockholm University, AlbaNova University Centre, 106 91 Stockholm, Sweden
ESO, Karl Schwarzchild Str. 2, 85748 Garching bei München, Germany
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European Southern Observatory · Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
ESO, Karl Schwarzchild Str. 2, 85748 Garching bei München, Germany
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
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Arcetri Astrophysical Observatory · National Institute for Astrophysics · University of Bologna
Affiliation as printed
DIFA, Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory, 1011 Lopezville Rd, Socorro, NM 87801, USA
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
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Harvard University · Universidad Nacional Autónoma de México
Affiliation as printed
Black Hole Initiative at Harvard University, 20 Garden Street, Cambridge, MA 02138, USA
David Rockefeller Center for Latin American Studies, Harvard University, 1730 Cambridge Street, Cambridge, MA 02138, USA
Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, A.P. 3-72 (Xangari), 8701 Morelia, Mexico
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Centre National de la Recherche Scientifique · Institut de Radioastronomie Millimétrique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-d’Hères, France
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory, 1011 Lopezville Rd, Socorro, NM 87801, USA
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Affiliation as printed
The Institute of Physical and Chemical Research (RIKEN), 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
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Affiliation as printed
Department of Astronomy, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 23000 RA Leiden, The Netherlands
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Affiliation as printed
ESO, Karl Schwarzchild Str. 2, 85748 Garching bei München, Germany
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Center for Astrochemical Studies, Max-Planck-Institut für Extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching, Germany
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Affiliation as printed
Astrochemistry Laboratory, Code 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
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Affiliation as printed
Centro de Astrobiología (CAB), INTA-CSIC, Carretera de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
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Herzberg Institute of Astrophysics · University of Victoria
Affiliation as printed
Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2, Canada
NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
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Arcetri Astrophysical Observatory · National Institute for Astrophysics
Affiliation as printed
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
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Affiliation as printed
Steward Observatory, 933 N Cherry Ave., Tucson, AZ 85721, USA
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The Graduate University for Advanced Studies, SOKENDAI
Affiliation as printed
The Graduate University for Advanced Studies (SOKENDAI), Shonan Village, Hayama, Kanagawa 240-0193, Japan
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