FAUST – XXIX. OCS line emission: a new method for measuring the luminosity of embedded protostars in binary systems
ABSTRACT The luminosity of embedded protostars is commonly measured via observations of the dust continuum spectral energy distribution from millimetre to infrared wavelengths. However, this method cannot be applied to embedded protostars in binary or multiple systems, where their components are usually unresolved over this extended wavelength range. We propose a new method, based on the idea that a molecule formed (mainly) on the grain surfaces only emits lines in the region where it thermally sublimates from the grain mantles, heated by the photons emitted by the embedded source. In this respect, carbonyl sulfide (OCS) is an optimal molecule, because of its low binding energy and rotational lines in the millimetre. We apply the method to the protobinary system NGC1333 IRAS4A, using ALMA high-spatial resolution ($\sim$50 au) observations of the OCS(19-18) line as part of the ALMA Large Programme FAUST. We also present new quantum mechanics calculations of the OCS binding energy distribution, essential for the application of the method. We found that the two binary components, A1 and A2, have a comparable luminosity within the error bars, 7.5 $\pm$ 2.5 and 7 $\pm$ 1 L$_\odot$, respectively. We discuss the reliability of the estimated luminosities and the potential of this new method for measuring the luminosity of embedded protostars in binary and multiple systems.
Authors
- Romane Le Gal (ORCID: https://orcid.org/0000-0003-1837-3772)
- Z. Zhang (ORCID: https://orcid.org/0000-0002-9927-2705)
- Mathilde Bouvier (ORCID: https://orcid.org/0000-0003-0167-0746)
- Layal Chahine (ORCID: https://orcid.org/0000-0003-3364-5094)
- Laurent Loinard (ORCID: https://orcid.org/0000-0002-5635-3345)
- Piero Ugliengo (ORCID: https://orcid.org/0000-0001-8886-9832)
- L. Podio (ORCID: https://orcid.org/0000-0003-2733-5372)
- G. Sabatini (ORCID: https://orcid.org/0000-0002-6428-9806)
- A. López-Sepulcre (ORCID: https://orcid.org/0000-0002-6729-3640)
- Albert Rimola (ORCID: https://orcid.org/0000-0002-9637-4554)
- Nami Sakai (ORCID: https://orcid.org/0000-0002-3297-4497)
- C. J. Chandler (ORCID: https://orcid.org/0000-0002-7570-5596)
- M. De Simone (ORCID: https://orcid.org/0000-0001-5659-0140)
- C. Codella (ORCID: https://orcid.org/0000-0003-1514-3074)
- Yoko Oya (ORCID: https://orcid.org/0000-0002-0197-8751)
- C. Vastel (ORCID: https://orcid.org/0000-0001-8211-6469)
- E. Bianchi (ORCID: https://orcid.org/0000-0001-9249-7082)
- C. Ceccarelli (ORCID: https://orcid.org/0000-0001-9664-6292)
- Vittorio Bariosco (ORCID: https://orcid.org/0009-0000-7269-8418)
- S. Yamamoto (ORCID: https://orcid.org/0000-0001-8984-9243)
- Lise Boitard–Crépeau
- Guillaume Saury
Institutions
- Leiden University (NL)
- Universitat Autònoma de Barcelona (ES)
- Centre National de la Recherche Scientifique (FR)
- Woodwell Climate Research Center (US)
- European Southern Observatory (DE)
- Université Toulouse III - Paul Sabatier (FR)
- Harvard University (US)
- Pioneer (United States) (US)
- Université Fédérale de Toulouse Midi-Pyrénées (FR)
- The Graduate University for Advanced Studies, SOKENDAI (JP)
- Kyoto University (JP)
- National Radio Astronomy Observatory (US)
- Arcetri Astrophysical Observatory (IT)
- Institut de Radioastronomie Millimétrique (FR)
- RIKEN (JP)
- University of Turin (IT)
- Universidad Nacional Autónoma de México (MX)
- Université Grenoble Alpes (FR)
Publication Details
- Journal
- Monthly Notices of the Royal Astronomical Society
- Published
- 2025-12-03
- DOI
- https://doi.org/10.1093/mnras/staf2157
- Primary Topic
- Astrophysics and Star Formation Studies
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- National Radio Astronomy Observatory
- Dipartimenti di Eccellenza
- European Commission
- National Science Council
- National Astronomical Observatory of Japan
- Ministero dell'Università e della Ricerca
- National Institutes of Natural Sciences