The Discovery of 25 <i>μ</i>m Interstellar Methanol
Abstract We present the first astrophysical detection of methanol (CH 3 OH) in the torsional band near 25 μ m. Using high-resolution mid-infrared (MIR) spectroscopy, we identified over 70 gas-phase CH 3 OH absorption lines between 20 and 28 μ m toward the massive protostar NGC 7538 IRS 1 with the Stratospheric Observatory for Infrared Astronomy/Echelon-Cross-Echelle Spectrograph. We derive a temperature of 180 K and a total column density of 2 × 10 17 cm −2 , comparable to submillimeter measurements. Complementary analysis of acetylene (C 2 H 2 ) absorption lines is also included. Both CH 3 OH and C 2 H 2 reveal an unresolved second velocity component. These MIR absorption lines likely probe the molecular material in two edge-on disks, supporting the scenario that NGC 7538 IRS 1 consists of multiple protostars. We provide an updated line list for the torsional band of CH 3 OH, which was generated from lab work and model calculations. This discovery and the updated line list will enable the search for CH 3 OH in JWST/MIRI spectra.
Authors
- William D. Vacca (ORCID: https://orcid.org/0000-0002-9123-0068)
- Clara Sousa‐Silva (ORCID: https://orcid.org/0000-0002-7853-6871)
- Edward Montiel (ORCID: https://orcid.org/0000-0003-2553-4474)
- Xinchuan Huang (ORCID: https://orcid.org/0000-0003-2458-5050)
- C. A. Nixon (ORCID: https://orcid.org/0000-0001-9540-9121)
- Jason Dittmann (ORCID: https://orcid.org/0000-0001-7730-2240)
- G. M. Harper (ORCID: https://orcid.org/0000-0002-7042-4541)
- J. P. Fonfría (ORCID: https://orcid.org/0000-0002-6556-6692)
- Naseem Rangwala (ORCID: https://orcid.org/0000-0001-9920-7391)
- Keeyoon Sung (ORCID: https://orcid.org/0000-0002-8030-7410)
- Sean W. J. Colgan (ORCID: https://orcid.org/0000-0001-6275-7437)
- Sarah Nickerson (ORCID: https://orcid.org/0000-0002-7489-3142)
- Valentin J. M. Le Gouellec (ORCID: https://orcid.org/0000-0002-5714-799X)
- A. G. G. M. Tielens (ORCID: https://orcid.org/0000-0003-0306-0028)
- K. E. Kraemer (ORCID: https://orcid.org/0000-0002-2626-7155)
- Curtis DeWitt (ORCID: https://orcid.org/0000-0002-6528-3836)
- Maisie Rashman (ORCID: https://orcid.org/0000-0002-3936-2469)
- Jialu Li (ORCID: https://orcid.org/0000-0003-0665-6505)
Publication Details
- Journal
- The Astrophysical Journal Letters
- Published
- 2025-08-20
- DOI
- https://doi.org/10.3847/2041-8213/adf632
- Primary Topic
- Spectroscopy and Laser Applications
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Aeronautics and Space Administration
- California Institute of Technology
- Universities Space Research Association
- Nuclear Safety and Security Commission
- Universität Stuttgart
- Jet Propulsion Laboratory