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Peer-reviewedCC BY 4.0Astronomy & Astrophysics

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)

  • H.-S. Yun1,2
  • J.-E. Lee1,3
  • J. K. Jørgensen4
  • A. Coutens5
  • A. L. Plunkett6
  • M. N. Drozdovskaya7,8
  • A. Belloche9
  • J.-H. Jeong1
  • P. Nazari10
  • Y.-L. Yang11
  • M. L. R. van ’t Hoff12
  • S. Maret13
7 more authors
  • F. Cruz-Sáenz de Miera5
  • D. Harsono14
  • C.-H. Kim1
  • Á. Kóspál15,16,17
  • M. Lützen4
  • S. Spezzano18
  • S. Zeng11
18 affiliations
  1. 1Department of Physics and Astronomy, Seoul National University
  2. 2Korea Astronomy and Space Science Institute
  3. 3SNU Astronomy Research Center, Seoul National University
  4. 4Niels Bohr Institute, University of Copenhagen
  5. 5Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, CNES
  6. 6National Radio Astronomy Observatory
  7. 7Physikalisch-Meteorologisches Observatorium Davos und Weltstrahlungszentrum (PMOD/WRC)
  8. 8Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP), Universität Bern
  9. 9Max-Planck-Institut für Radioastronomie
  10. 10European Southern Observatory
  11. 11Star and Planet Formation Laboratory, RIKEN Pioneering Research Institute, Wako-shi
  12. 12Purdue University
  13. 13Univ. Grenoble Alpes, CNRS, IPAG
  14. 14Institute of Astronomy, Department of Physics, National Tsing Hua University
  15. 15Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence
  16. 16Institute of Physics and Astronomy, ELTE Eötvös Loránd University
  17. 17Max-Planck-Institut für Astronomie
  18. 18Max-Planck-Institut für extraterrestrische Physik
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Abstract

Context . Complex organic molecules (COMs) are detected in the interstellar medium, both in cold molecular clouds and in the warm inner regions of protostars. Whether these COMs are eventually directly inherited by protostars and planets or whether their chemistry is reset by in situ reactions remains unclear. Recent (sub)millimeter wavelength observations have spatially resolved the emission of gas-phase COMs around low-mass protostars, not only in compact hot corinos but also in the extended structures beyond them. Understanding the physical properties and desorption mechanisms of these molecules is essential for tracing their chemical evolution during the protostellar evolutionary sequence. Methanol (CH ₃ OH), the most abundant COM in star-forming regions, serves as an ideal tracer for investigating these processes.

Aims . As part of the ALMA Cycle 9 Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS), we investigate the CH ₃ OH emission that extends beyond the hot corino of the low-mass protostar BHR71-IRS1.

Methods . We identified spatially extended emission of CH ₃ OH around BHR71-IRS1 and subsequently explored plausible desorption scenarios. We assessed characteristic emission structures by applying a principal component analysis (PCA) to the identified emission lines. The physical properties of their line-emitting gas were derived under the local thermodynamic equilibrium (LTE) assumption through both rotational diagram and spectral modeling analyses.

Results . In total, 26 spatially extended CH ₃ OH lines have been detected around BHR71-IRS1. These emission lines are distributed across three distinct structures: (1) X-shaped cavity walls, (2) compact northern and southern shocked knots, and (3) additional distant eastern and southeastern components. The cavity walls exhibit excitation temperatures of ∼25 K and column densities of ∼10 ¹⁴ cm ⁻² , while the knots show relatively higher excitation temperatures (70–120 K) and column densities (10 ¹⁴ –10 ¹⁶ cm ⁻² ). The eastern and southeastern components appear unrelated to BHR71-IRS1, and their physical properties are not well constrained under LTE conditions, suggesting that a non-LTE analysis may be required.

Conclusions . Plausible desorption mechanisms are evaluated by comparing the physical parameters with model predictions that simulated the effects of far-ultraviolet (FUV) photons and C-type shocks. The low excitation temperatures and narrow line widths (∼0.7 km s ⁻¹ ) in the cavity walls favor a reactive desorption scenario driven by FUV irradiation from IRS1. In contrast, the knots with higher excitation temperatures and column densities support the dust sputtering scenario induced by C-type shocks.

Related

  1. Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS). VIII. First interstellar detection of fully deuterated methyl cyanide
    A. Belloche, J. K. Jorgensen, M. N. Drozdovskaya +12
    Astronomy & AstrophysicsPeer-reviewedPublisher termsSolar & stellar physicsCrossref
  2. Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) VII. First interstellar detection of fully deuterated methanol
    A. Belloche, S. Spezzano, A. Coutens +12
    arXivPreprintarXiv licenceFull textGalaxiesarXiv
  3. Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) VIII. First interstellar detection of fully deuterated methyl cyanide
    A. Belloche, J. K. Jørgensen, M. N. Drozdovskaya +12
    arXivPreprintarXiv licenceFull textGalaxiesarXiv
  4. Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) V. Tracing cavity walls and shocked knots with nonthermally desorbed CH3OH in BHR71-IRS1
    H. -S. Yun, J. -E. Lee, J. K. Jørgensen +16
    arXivPreprintCC BY-NC-SA 4.0Full textGalaxiesarXiv

Cite

BibTeXRIS
BibTeX
@article{yun2026complex,
  title = {{Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)}},
  author = {H.-S. Yun and J.-E. Lee and J. K. Jørgensen and A. Coutens and A. L. Plunkett and M. N. Drozdovskaya and A. Belloche and J.-H. Jeong and P. Nazari and Y.-L. Yang and M. L. R. van ’t Hoff and S. Maret and F. Cruz-Sáenz de Miera and D. Harsono and C.-H. Kim and Á. Kóspál and M. Lützen and S. Spezzano and S. Zeng},
  journal = {Astronomy \& Astrophysics},
  year = {2026},
  month = oct,
  doi = {10.1051/0004-6361/202558732},
  url = {https://www.aanda.org/10.1051/0004-6361/202558732},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)
AU  - H.-S. Yun
AU  - J.-E. Lee
AU  - J. K. Jørgensen
AU  - A. Coutens
AU  - A. L. Plunkett
AU  - M. N. Drozdovskaya
AU  - A. Belloche
AU  - J.-H. Jeong
AU  - P. Nazari
AU  - Y.-L. Yang
AU  - M. L. R. van ’t Hoff
AU  - S. Maret
AU  - F. Cruz-Sáenz de Miera
AU  - D. Harsono
AU  - C.-H. Kim
AU  - Á. Kóspál
AU  - M. Lützen
AU  - S. Spezzano
AU  - S. Zeng
PY  - 2026
DA  - 2026/10/07
JO  - Astronomy & Astrophysics
DO  - 10.1051/0004-6361/202558732
UR  - https://www.aanda.org/10.1051/0004-6361/202558732
AB  - Context . Complex organic molecules (COMs) are detected in the interstellar medium, both in cold molecular clouds and in the warm inner regions of protostars. Whether these COMs are eventually directly inherited by protostars and planets or whether their chemistry is reset by in situ reactions remains unclear. Recent (sub)millimeter wavelength observations have spatially resolved the emission of gas-phase COMs around low-mass protostars, not only in compact hot corinos but also in the extended structures beyond them. Understanding the physical properties and desorption mechanisms of these molecules is essential for tracing their chemical evolution during the protostellar evolutionary sequence. Methanol (CH ₃ OH), the most abundant COM in star-forming regions, serves as an ideal tracer for investigating these processes.  Aims . As part of the ALMA Cycle 9 Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS), we investigate the CH ₃ OH emission that extends beyond the hot corino of the low-mass protostar BHR71-IRS1.  Methods . We identified spatially extended emission of CH ₃ OH around BHR71-IRS1 and subsequently explored plausible desorption scenarios. We assessed characteristic emission structures by applying a principal component analysis (PCA) to the identified emission lines. The physical properties of their line-emitting gas were derived under the local thermodynamic equilibrium (LTE) assumption through both rotational diagram and spectral modeling analyses.  Results . In total, 26 spatially extended CH ₃ OH lines have been detected around BHR71-IRS1. These emission lines are distributed across three distinct structures: (1) X-shaped cavity walls, (2) compact northern and southern shocked knots, and (3) additional distant eastern and southeastern components. The cavity walls exhibit excitation temperatures of ∼25 K and column densities of ∼10 ¹⁴ cm ⁻² , while the knots show relatively higher excitation temperatures (70–120 K) and column densities (10 ¹⁴ –10 ¹⁶ cm ⁻² ). The eastern and southeastern components appear unrelated to BHR71-IRS1, and their physical properties are not well constrained under LTE conditions, suggesting that a non-LTE analysis may be required.  Conclusions . Plausible desorption mechanisms are evaluated by comparing the physical parameters with model predictions that simulated the effects of far-ultraviolet (FUV) photons and C-type shocks. The low excitation temperatures and narrow line widths (∼0.7 km s ⁻¹ ) in the cavity walls favor a reactive desorption scenario driven by FUV irradiation from IRS1. In contrast, the knots with higher excitation temperatures and column densities support the dust sputtering scenario induced by C-type shocks.
SN  - 0004-6361
SN  - 1432-0746
ER  -