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Published online by Cambridge University Press: 25 May 2016
Elevated ratios of [S II]/Hα relative to those typical of H II regions have been used to identify supernova remnants (SNRs) and also characterize the diffuse Galactic background (Reynolds 1985) and gas observed on the large scale in other galaxies (e.g., Lehnert & Heckman 1994). We explore the implications for these regions of the fact that ionized sulfur may exist both in gas that is predominantly neutral as well as fully ionized.