Abstract
We report the discovery of a widespread population of collisionally excited methanol J = 4-1 to 30 E sources at 36.2 GHz from the inner 66′ × 18′ (160 × 43 pc) of the Galactic center. This spectral feature was imaged with a spectral resolution of 16.6 km s -1 taken from 41 channels of a Very Large Array continuum survey of the Galactic center region. The revelation of 356 methanol sources, most of which are maser candidates, suggests a large abundance of methanol in the gas phase in the Galactic center region. There is also spatial and kinematic correlation between SiO (2-1) and CH3OH emission from four Galactic center clouds: the +50 and +20 km s-1 clouds and G0.13-0.13 and G0.25 + 0.01. The enhanced abundance of methanol is accounted for in terms of induced photodesorption by cosmic rays as they travel through a molecular core, collide, dissociate, ionize, and excite Lyman Werner transitions of H 2. A time-dependent chemical model in which cosmic rays drive the chemistry of the gas predicts CH3OH abundance of 10-8 to 10-7 on a chemical timescale of 5 × 104 to 5 × 105 years. The average methanol abundance produced by the release of methanol from grain surfaces is consistent with the available data.
Original language | English (US) |
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Article number | L19 |
Journal | Astrophysical Journal Letters |
Volume | 764 |
Issue number | 2 |
DOIs | |
State | Published - Feb 20 2013 |
Keywords
- Galaxy: nucleus
- ISM: molecules
- astrochemistry
- cosmic rays
- masers
- stars: early-type
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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Methanol emission from the Galactic Center
Yusef-Zadeh, F. (Creator), Cotton, W. (Creator), Viti, S. (Creator), Wardle, M. (Creator) & Royster, M. (Creator), Centre de Donnees Strasbourg (CDS), 2014
DOI: 10.26093/cds/vizier.17649019, https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/764/L19
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