Year: 2025
Type: article
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 (CH3OH, HCOOCH3, CH3CHO, CH3CH2OH, CH2OHCHO, and NH2CHO), 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 CH3OH, 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 NH2CHO and CH2OHCHO, followed by CH3CH2OH (∼27 au), CH3CHO (∼28 au), HCOOCH3 (∼36 au), and out to ∼40 au for CH3OH. 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: J. Frediani, M. De Simone, L. Testi, L. Podio, C. Codella, C. J. Chandler, C. Ceccarelli, L. Loinard, A. López-Sepulcre, B. Svoboda, N. Sakai, L. Chahine, Y. Aikawa, E. Bianchi, M. Bouvier, L. Cacciapuoti, P. Caselli, S. B. Charnley, I. Jimenez-Serra, D. Johnstone, G. Sabatini, Y. Shirley, S. Yamamoto
Institutions: European Southern Observatory, Arcetri Astrophysical Observatory, University of Bologna, National Radio Astronomy Observatory, Centre National de la Recherche Scientifique, Institut de Planétologie et d'Astrophysique de Grenoble, Institut de Radioastronomie Millimétrique, RIKEN, The University of Tokyo, Leiden University, Leiden Observatory, Max Planck Institute for Extraterrestrial Physics, Goddard Space Flight Center, Centro de Astrobiología, Herzberg Institute of Astrophysics, University of Victoria, University of Arizona, The Graduate University for Advanced Studies, SOKENDAI
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, National Radio Astronomy Observatory, European Commission, National Science Council, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, European Regional Development Fund, Agencia Estatal de Investigación, Planetary Science Division, H2020 European Research Council
Awards: G1507096846, G1743472294, G2262748287, G2340603345, G3055077951, G3480869486, G3681454997, Understanding our Galactic ecosystem: From the disk of the Milky Way to the formation sites of stars and planets, G4042783231, G425668148, G451917667, Dust and gas in planet forming discs, G5967599077, G923063681
OpenAlex ID: W6959603104
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