Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)
17 affiliations
- 1European Southern Observatory
- 2Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, CNES
- 3Niels Bohr Institute, University of Copenhagen
- 4Max-Planck-Institut für Radioastronomie
- 5National Radio Astronomy Observatory
- 6Univ. Grenoble Alpes, CNRS, IPAG
- 7Institute of Astronomy, Department of Physics, National Tsinghua University
- 8Physikalisch-Meteorologisches Observatorium Davos und Weltstrahlungszentrum (PMOD/WRC)
- 9Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP), Universität Bern
- 10Department of Physics and Astronomy, Seoul National University
- 11Star and Planet Formation Laboratory, RIKEN Pioneering Research Institute, Wako-shi
- 12Purdue University
- 13Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence
- 14Institute of Physics and Astronomy, ELTE Eötvös Loránd University
- 15Max-Planck-Insitut für Astronomie
- 16Department of Chemistry, Massachusetts Institute of Technology and National Radio Astronomy Observatory
- 17Max-Planck-Institut für extraterrestrische Physik
Abstract
Context . Methyl cyanide (CH ₃ CN) is one of the most abundant nitrogen-bearing complex organic molecules observed in the gas phase around both low- and high-mass protostars. However, very few observations exist with a broad enough frequency coverage and sufficiently high sensitivity to systematically characterize its minor isotopologues toward such regions.
Aims . We add to this number by analyzing data toward BHR71-IRS1 taken with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) Large Program over a ∼33 GHz frequency range.
Methods . We studied as many isotopologues of methyl cyanide as possible toward BHR71-IRS1. We found the column densities and excitation temperatures via spectral fitting and assuming local thermodynamic equilibrium. We then compared the derived column density ratios with those toward IRAS 16293-2422 A and B, V883 Ori, G31.41+0.31, and Sgr B2(N2b).
Results . We detect CH ₃ CN, CH ₃ CN v ₈ =1, ¹³ CH ₃ CN, CH ₃ ¹³ CN, CH ₃ C ¹⁵ N, CH ₂ DCN, and CHD ₂ CN. The column density ratio of ¹³ CH ₃ CN/CH ₃ ¹³ CN is around unity, in agreement with previous observations. The CH ₂ DCN/CH ₃ CN ratios are similar for all the low-mass objects but are ∼1 order of magnitude higher than those toward Sgr B2(N2b). This could be due to a warmer pre-stellar phase or a different formation timescale of Sgr B2(N2b).
Conclusions . The D/H ratios found from methyl cyanide isotopologues agree well with those of methanol toward BHR71-IRS1, likely pointing to the formation and deuteration of methyl cyanide in a similar star-formation phase as methanol (i.e., the pre-stellar phase). We find an increase in the methyl cyanide D/H ratios with the number of deuterium atoms, which suggests that the deuterated isotopologues may form later in the pre-stellar phase. Future COMPASS studies will increase the sample size of low-mass systems with methyl cyanide analysis and potentially examine some of the trends observed here statistically.
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{nazari2026complex,
title = {{Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)}},
author = {P. Nazari and A. Coutens and J. K. Jørgensen and A. Belloche and A. L. Plunkett and S. Maret and D. Harsono and M. N. Drozdovskaya and J.-E. Lee and F. Cruz-Sáenz de Miera and J. Ferrer Asensio and M. L. R. van ’t Hoff and J.-H. Jeong and Á. Kóspál and B. A. McGuire and S. Spezzano and Y.-L. Yang and H.-S. Yun and S. Zeng},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202558748},
url = {https://www.aanda.org/10.1051/0004-6361/202558748},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)
AU - P. Nazari
AU - A. Coutens
AU - J. K. Jørgensen
AU - A. Belloche
AU - A. L. Plunkett
AU - S. Maret
AU - D. Harsono
AU - M. N. Drozdovskaya
AU - J.-E. Lee
AU - F. Cruz-Sáenz de Miera
AU - J. Ferrer Asensio
AU - M. L. R. van ’t Hoff
AU - J.-H. Jeong
AU - Á. Kóspál
AU - B. A. McGuire
AU - S. Spezzano
AU - Y.-L. Yang
AU - H.-S. Yun
AU - S. Zeng
PY - 2026
DA - 2026/10/07
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202558748
UR - https://www.aanda.org/10.1051/0004-6361/202558748
AB - Context . Methyl cyanide (CH ₃ CN) is one of the most abundant nitrogen-bearing complex organic molecules observed in the gas phase around both low- and high-mass protostars. However, very few observations exist with a broad enough frequency coverage and sufficiently high sensitivity to systematically characterize its minor isotopologues toward such regions. Aims . We add to this number by analyzing data toward BHR71-IRS1 taken with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) Large Program over a ∼33 GHz frequency range. Methods . We studied as many isotopologues of methyl cyanide as possible toward BHR71-IRS1. We found the column densities and excitation temperatures via spectral fitting and assuming local thermodynamic equilibrium. We then compared the derived column density ratios with those toward IRAS 16293-2422 A and B, V883 Ori, G31.41+0.31, and Sgr B2(N2b). Results . We detect CH ₃ CN, CH ₃ CN v ₈ =1, ¹³ CH ₃ CN, CH ₃ ¹³ CN, CH ₃ C ¹⁵ N, CH ₂ DCN, and CHD ₂ CN. The column density ratio of ¹³ CH ₃ CN/CH ₃ ¹³ CN is around unity, in agreement with previous observations. The CH ₂ DCN/CH ₃ CN ratios are similar for all the low-mass objects but are ∼1 order of magnitude higher than those toward Sgr B2(N2b). This could be due to a warmer pre-stellar phase or a different formation timescale of Sgr B2(N2b). Conclusions . The D/H ratios found from methyl cyanide isotopologues agree well with those of methanol toward BHR71-IRS1, likely pointing to the formation and deuteration of methyl cyanide in a similar star-formation phase as methanol (i.e., the pre-stellar phase). We find an increase in the methyl cyanide D/H ratios with the number of deuterium atoms, which suggests that the deuterated isotopologues may form later in the pre-stellar phase. Future COMPASS studies will increase the sample size of low-mass systems with methyl cyanide analysis and potentially examine some of the trends observed here statistically.
SN - 0004-6361
SN - 1432-0746
ER -