The Discovery of 25 μm Interstellar Methanol
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 Stratosph...
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| Main Authors: | , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/adf632 |
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| Summary: | 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. |
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| ISSN: | 2041-8205 |