Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)
18 affiliations
- 1Department of Physics and Astronomy, Seoul National University
- 2Niels Bohr Institute, University of Copenhagen
- 3Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, CNES
- 4Physikalisch-Meteorologisches Observatorium Davos und Weltstrahlungszentrum (PMOD/WRC)
- 5Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP), Universität Bern
- 6National Radio Astronomy Observatory
- 7Max-Planck-Institut für Radioastronomie
- 8Institut de Planétologie et d’Astrophysique de Grenoble, Univ. Grenoble Alpes, CNRS, IPAG
- 9Korea Astronomy and Space Science Institute
- 10Institute of Astronomy, Department of Physics, National Tsinghua University
- 11Department of Physics and Astronomy, Purdue University
- 12Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence
- 13Institute of Physics and Astronomy, ELTE Eötvös Loránd University
- 14Max-Planck-Institut für Astronomie
- 15Department of Chemistry, Massachusetts Institute of Technology
- 16European Southern Observatory
- 17Max-Planck-Institut für extraterrestrische Physik
- 18Star and Planet Formation Laboratory, RIKEN Pioneering Research Institute, Wako-shi
Abstract
Context . Methanol (CH ₃ OH) masers that are collisionally pumped, referred to as ‘class I’, commonly trace shock interfaces in star-forming regions, but their incidence in embedded low-mass protostars remains poorly quantified.
Aims . We aim to (i) establish the occurrence, spatial origin, and excitation of a newly detected class I CH ₃ OH maser at 302.913 GHz (12 0,12 –11 1,11 A, E u = 180.9 K) towards low-mass protostars and (ii) test whether the environments that pump this maser exhibit signatures of shock-driven complex chemistry.
Methods . We utilised data from the COMPASS ALMA Large Program to search for maser activity in the 302.9 GHz line in a sample of 11 low-mass protostellar sources. The COMPASS programme provides unbiased surveys of these sources between 279.0 and 311.7 GHz covering several transitions of CH ₃ OH as well as other complex organic molecules (COMs) at typical angular resolutions of 0.″3 − −0.″5. Measuring departures from local thermodynamic equilibrium (LTE) in the 302.9 GHz CH ₃ OH excitation via rotation diagram analysis robustly revealed masing.
Results . The 302.9 GHz CH ₃ OH line is detected as a non-thermal excess (maser) in seven out of 11 COMPASS sources, with peak brightness temperatures ranging from a few to a thousand kelvin. One of these detections is towards HOPS 108, which hosts the brightest maser, and it is likely associated with the powerful outflow driven by the nearby intermediate-mass protostar HOPS 370. Excluding this case, the maser is detected in six of the ten low-mass protostars (60%). All six low-mass protostars in which maser emission is detected are Class 0 sources interacting with dense ambient material, whereas non-detections correspond to three Class I objects and one isolated Class 0 core. This indicates a preference for early evolutionary stages and environments rich in gas for outflow–ambient medium interactions. The maser emission is spatially coincident with thermal CH ₃ OH emission along the outflow cavity walls and bow shocks, but it has more compact knot-like morphologies. Lastly, among the surveyed COMs, only acetaldehyde (CH ₃ CHO) closely traces the shocked morphology of the 302.9 GHz CH ₃ OH maser. However, this CH ₃ CHO feature is observed only towards the brightest maser in the region around HOPS 108, which is influenced by the intermediate-mass protostellar outflow.
Conclusions . Our study reveals that class I CH ₃ OH masers in low-mass protostellar systems are more prevalent than previously recognised and preferentially occur in younger, more embedded systems. Although this has only been observed in an intermediate-mass protostellar outflow, CH ₃ CHO is enhanced in a manner consistent with shock-driven chemistry along the outflow cavities. Testing whether a similar relationship applies in the low-mass regime will require more sensitive CH ₃ CHO observations towards regions where the class I CH ₃ OH masers are detected.
Related
- Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS). VIII. First interstellar detection of fully deuterated methyl cyanide
- Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) VII. First interstellar detection of fully deuterated methanol
- Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) VIII. First interstellar detection of fully deuterated methyl cyanide
- Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) V. Tracing cavity walls and shocked knots with nonthermally desorbed CH3OH in BHR71-IRS1
BibTeX
@article{jeong2026complex,
title = {{Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)}},
author = {Jae-Hong Jeong and Jeong-Eun Lee and Jes K. Jørgensen and Audrey Coutens and Maria N. Drozdovskaya and Adele L. Plunkett and Arnaud Belloche and Sébastien Maret and Hyeong-Sik Yun and Fernando Cruz-Sáenz de Miera and Daniel Harsono and Merel L. R. van ’t Hoff and Chul-Hwan Kim and Ágnes Kóspál and Brett A. McGuire and Pooneh Nazari and Silvia Spezzano and Yao-Lun Yang and Shaoshan Zeng},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202558734},
url = {https://www.aanda.org/10.1051/0004-6361/202558734},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)
AU - Jae-Hong Jeong
AU - Jeong-Eun Lee
AU - Jes K. Jørgensen
AU - Audrey Coutens
AU - Maria N. Drozdovskaya
AU - Adele L. Plunkett
AU - Arnaud Belloche
AU - Sébastien Maret
AU - Hyeong-Sik Yun
AU - Fernando Cruz-Sáenz de Miera
AU - Daniel Harsono
AU - Merel L. R. van ’t Hoff
AU - Chul-Hwan Kim
AU - Ágnes Kóspál
AU - Brett A. McGuire
AU - Pooneh Nazari
AU - Silvia Spezzano
AU - Yao-Lun Yang
AU - Shaoshan Zeng
PY - 2026
DA - 2026/10/07
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202558734
UR - https://www.aanda.org/10.1051/0004-6361/202558734
AB - Context . Methanol (CH ₃ OH) masers that are collisionally pumped, referred to as ‘class I’, commonly trace shock interfaces in star-forming regions, but their incidence in embedded low-mass protostars remains poorly quantified. Aims . We aim to (i) establish the occurrence, spatial origin, and excitation of a newly detected class I CH ₃ OH maser at 302.913 GHz (12 0,12 –11 1,11 A, E u = 180.9 K) towards low-mass protostars and (ii) test whether the environments that pump this maser exhibit signatures of shock-driven complex chemistry. Methods . We utilised data from the COMPASS ALMA Large Program to search for maser activity in the 302.9 GHz line in a sample of 11 low-mass protostellar sources. The COMPASS programme provides unbiased surveys of these sources between 279.0 and 311.7 GHz covering several transitions of CH ₃ OH as well as other complex organic molecules (COMs) at typical angular resolutions of 0.″3 − −0.″5. Measuring departures from local thermodynamic equilibrium (LTE) in the 302.9 GHz CH ₃ OH excitation via rotation diagram analysis robustly revealed masing. Results . The 302.9 GHz CH ₃ OH line is detected as a non-thermal excess (maser) in seven out of 11 COMPASS sources, with peak brightness temperatures ranging from a few to a thousand kelvin. One of these detections is towards HOPS 108, which hosts the brightest maser, and it is likely associated with the powerful outflow driven by the nearby intermediate-mass protostar HOPS 370. Excluding this case, the maser is detected in six of the ten low-mass protostars (60%). All six low-mass protostars in which maser emission is detected are Class 0 sources interacting with dense ambient material, whereas non-detections correspond to three Class I objects and one isolated Class 0 core. This indicates a preference for early evolutionary stages and environments rich in gas for outflow–ambient medium interactions. The maser emission is spatially coincident with thermal CH ₃ OH emission along the outflow cavity walls and bow shocks, but it has more compact knot-like morphologies. Lastly, among the surveyed COMs, only acetaldehyde (CH ₃ CHO) closely traces the shocked morphology of the 302.9 GHz CH ₃ OH maser. However, this CH ₃ CHO feature is observed only towards the brightest maser in the region around HOPS 108, which is influenced by the intermediate-mass protostellar outflow. Conclusions . Our study reveals that class I CH ₃ OH masers in low-mass protostellar systems are more prevalent than previously recognised and preferentially occur in younger, more embedded systems. Although this has only been observed in an intermediate-mass protostellar outflow, CH ₃ CHO is enhanced in a manner consistent with shock-driven chemistry along the outflow cavities. Testing whether a similar relationship applies in the low-mass regime will require more sensitive CH ₃ CHO observations towards regions where the class I CH ₃ OH masers are detected.
SN - 0004-6361
SN - 1432-0746
ER -