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Class I Methanol Masers in the Galactic Center

Published online by Cambridge University Press:  24 July 2012

Loránt O. Sjouwerman  and
Ylva M. Pihlström
Loránt O. Sjouwerman
Affiliation:
National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Rd., Socorro, NM 87801
Ylva M. Pihlström
Affiliation:
Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131
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Abstract

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We report on 36 and 44 GHz Class I methanol (CH3OH) maser emission in the Sagittarius A (Sgr A) region with the Expanded Very Large Array (EVLA). At least three different maser transitions tracing shocked regions in the cm-wave radio regime can be found in Sgr A. 44 GHz masers correlate with the positions and velocities of 36 GHz CH3OH masers, but the methanol masers correlate less with 1720 MHz OH masers. Our results agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under cooler or denser conditions. We speculate that the geometry of the bright 36 GHz masers in Sgr A East outlines the location of a SNR shock front.

Keywords

Galaxy: center — Masers — Shock waves — Supernovae: individual(Sgr A East)
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S287: Cosmic Masers - from OH to H0 , January 2012 , pp. 449 - 454
Copyright
Copyright © International Astronomical Union 2012

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