Widespread methanol emission from the galactic center: The role of cosmic rays

F. Yusef-Zadeh*, W. Cotton, S. Viti, M. Wardle, M. Royster

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

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 languageEnglish (US)
Article numberL19
JournalAstrophysical Journal Letters
Volume764
Issue number2
DOIs
StatePublished - 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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