MAJORS II: HCO+and HCN abundances in W40
Plume R. Eden D.J. Currie M.J. Morgan L.K. Jiang X.-J. Difrancesco J. Imanishi M. Kim K.-T. Liu T. Rani R. Traficante A. Cohen J. Evans Ii N.J. Ho L.C. Chung E.J. Jiao S. Lee C.W. Alina D. Moore T. Rawlings J.M.C. Kirchschlager F. Patra S. Rigby A.J. Shang H. Hwang J. Sanhueza P. Rawlings M.G. Tahani K. Wang J. Pattle K. Urquhart J.S. Nguyen-Luong Q. Ragan S.E. Su Y. Tang X. Karska A. Burton M.G.
1 April 2026Oxford University Press
Monthly Notices of the Royal Astronomical Society
2026#547Issue 3
We present observations of HCN and HCO J = in the central region of the W40 massive star-forming region. The observations were taken as part of a pilot project for the MAJORS large program at the JCMT telescope. By incorporating prior knowledge of N(H) and, assuming a constant density, and using the radex radiative transfer code we found that the HCN and HCO abundances range from X(HCN) = and X(HCO) =. Additional modelling using the nautilus chemical evolution code, which takes H density variations into account, however, suggests that the HCN and HCO abundances may be fairly constant. Careful modelling of three different positions finds X(HCN) = and X(HCO) =. Cross-comparison of the two models also provides a crude estimate of the gas density producing the HCN and HCO emission, with H densities in the range - cm, suggesting that the HCN and HCO emission does indeed arise from dense gas. High UV intensity (e.g. $]]> a few thousand) has no effect on the abundances in regions where the visual extinction is large enough to effectively shield the gas from the UV field. In regions where, however, the abundance of both species is lowered due to destructive reactions with species that are directly affected by the radiation field.
ISM: abundances , ISM: clouds , ISM: molecules , stars: formation , surveys
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Department of Physics and Astronomy, University of Calgary, 2500 University Dr NW, Calgary, T2N 1N4, AB, Canada
Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
STFC RAL Space, Rutherford Appleton Laboratory, Harwell Campus Didcot, Oxfordshire, OX11 0QX, United Kingdom
Green Bank Observatory, 155 Observatory Rd, Green Bank, 24944, WV, United States
Research Centre for Astronomical Computing, Zhejiang Laboratory, Hangzhou, 311121, China
NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Rd, Victoria, V9E 2E7, BC, Canada
Department of Physics and Astronomy, University of Victoria, Victoria, V8W 2Y2, BC, Canada
National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo, 181-8588, Japan
Department of Astronomy, School of Science, Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo, 181-8588, Japan
Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejon, 34055, South Korea
University of Science and Technology Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, South Korea
Shanghai Astronomical Observatory, Shanghai, China
Institute of Astronomy, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan
IAPS - INAF, Via Fosso del Cavaliere, 100, Rome, I-00133, Italy
Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, 78712-1205, TX, United States
Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, 100871, China
Department of Astronomy, School of Physics, Peking University, Beijing, 100871, China
National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, 100012, China
Physics Department, Nazarbayev University, Astana, Kazakhstan
Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool, L3 5RF, United Kingdom
Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, United Kingdom
Sterrenkundig Observatorium, Ghent University, Krijgslaan 281-S9, Gent, B-9000, Belgium
Institute for Advanced Studies, Nicolaus Copernicus University in Torun, Wileńska 4, Toruń, PL-87-100, Poland
School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
Institute of Astronomy and Astrophysics, Academia Sinica: Taipei, Taiwan
Korea Astronomy and Space Science Institute (KASI), 776 Daedeokdae-ro, Yuseong-gu, Daejeon, 34055, South Korea
Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan
Gemini Observatory/NSF NOIRLab, 670 N. Aohōkū Place, Hilo, 96720, HI, United States
Department of Physics & Astronomy, Kwantlen Polytechnic University, 12666 72nd Avenue, Surrey, V3W 2M8, BC, Canada
Department of Astronomy, Xiamen University, Fujian, Xiamen, 361005, China
Centre for Astrophysics and Planetary Science, University of Kent, Canterbury, CT2 7NH, United Kingdom
Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, Gif-sur-Yvette, 91191, France
Cardiff Hub for Astrophysics Research & Technology, School of Physics & Astronomy, Cardiff University, Queens Buildings, Cardiff, CF24 3AA, United Kingdom
Purple Mountain Observatory, Yuanhua Road 10, Nanjing, 210023, China
Xinjiang Astronomical Observatory, CAS 150, Science 1-Street, Urumqi, 830011, China
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, D-53121, Germany
Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DB, United Kingdom
Department of Physics and Astronomy
Department of Physics
STFC RAL Space
Green Bank Observatory
Research Centre for Astronomical Computing
NRC Herzberg Astronomy and Astrophysics
Department of Physics and Astronomy
National Astronomical Observatory of Japan
Department of Astronomy
Korea Astronomy and Space Science Institute
University of Science and Technology Korea (UST)
Shanghai Astronomical Observatory
Institute of Astronomy
IAPS - INAF
Department of Astronomy
Kavli Institute for Astronomy and Astrophysics
Department of Astronomy
National Astronomical Observatories
Physics Department
Astrophysics Research Institute
Department of Physics and Astronomy
Sterrenkundig Observatorium
Institute for Advanced Studies
School of Physics and Astronomy
Institute of Astronomy and Astrophysics
Korea Astronomy and Space Science Institute (KASI)
Department of Astronomy
Gemini Observatory/NSF NOIRLab
Department of Physics & Astronomy
Department of Astronomy
Centre for Astrophysics and Planetary Science
Université Paris-Saclay
Cardiff Hub for Astrophysics Research & Technology
Purple Mountain Observatory
Xinjiang Astronomical Observatory
Max-Planck-Institut für Radioastronomie
Armagh Observatory and Planetarium
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