Hyperfine structure of the methanol molecule as traced by Class I methanol masers
Journal article, 2024

We present results on simultaneous observations of Class I methanol masers at 25, 36, and 44 GHz towards 22 Galactic targets carried out with the Effelsberg 100-m telescope. The study investigates relations between the hyperfine (HF) structure of the torsion–rotation transitions in CH3OH and maser activity. By analysing the radial velocity shifts between different maser lines together with the patterns of the HF structure based on laboratory measurements and quantum-chemical calculations, we find that in any source only one specific HF transition forms the maser emission and that this transition changes from source to source. The physical conditions leading to this selective behaviour are still unclear. Using accurate laboratory rest frequencies for the 25 GHz transitions, we have refined the centre frequencies for the HF multiplets at 36, 44, and 95 GHz: f36 = (36169.2488 ± 0.0002stat ± 0.0004sys) MHz. f44 = (44069.4176 ± 0.0002stat ± 0.0004sys) MHz, and f95 = (95169.4414 ± 0.0003stat ± 0.0004sys) MHz. Comparison with previous observations of 44 GHz masers performed 6–10 yr ago with a Korean 21-m Korean Very Long Baseline Interferometry Network telescope towards the same targets confirms the kinematic stability of Class I maser line profiles during this time interval and reveals a systematic radial velocity shift of 0.013 ± 0.005 km s−1 between the two telescopes.

methods: numerical

ISM: molecules

radio lines: ISM

elementary particles

techniques: spectroscopic

Author

I. I. Agafonova

Russian Academy of Sciences

O. S. Bayandina

Arcetri Astrophysical Observatory

Y. Gong

Chinese Academy of Sciences

Max Planck Society

C. Henkel

Xinjiang Astronomical Observatory

Max Planck Society

Kee-Tae Kim

University of Science and Technology (UST)

Korea Astronomy and Space Science Institute

M. G. Kozlov

Saint Petersburg Electrotechnical University

Petersburg Nuclear Physics Institute (PNPI)

Boy Lankhaar

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

S. A. Levshakov

Russian Academy of Sciences

K. Menten

Max Planck Society

W. Ubachs

Vrije Universiteit Amsterdam

I. E. Val'tts

Russian Academy of Sciences

W. Yang

Max Planck Society

Nanjing University

Monthly Notices of the Royal Astronomical Society

00358711 (ISSN) 13652966 (eISSN)

Vol. 533 2 1714-1732

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1093/mnras/stae1815

More information

Latest update

9/5/2024 1