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Collisional excitation of OH(6049 MHz) masers in supernova remnant – molecular cloud interactions

Published online by Cambridge University Press:  01 March 2007

Mark Wardle
Mark Wardle*
Affiliation:
Department of Physics, Macquarie University, Sydney, NSW 2109, Australia email: wardle@physics.mq.edu.au
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Abstract

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OH (1720 MHz) masers serve as indicators of SNR – molecular cloud interaction sites. These masers are collisionally excited in warm (50–100 K) shocked gas with densities of order 105cm−3 when the OH column density is in the range 1016−1017cm−2. Here I present excitation calculations which show that when the OH column density exceeds 1017cm−2 at similar densities and temperatures, the inversion of the 1720 MHz line switches off and instead the 6049 MHz transition in the first excited rotational state of OH becomes inverted. This line may serve as a complementary signal of warm, shocked gas when the OH column density is large.

Keywords

supernova remnantsmolecular processesradiation mechanisms: nonthermalradio lines: ISM

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