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Session 40 - The Interstellar Medium.
Display session, Tuesday, June 09
Atlas Ballroom,
We present a KPNO 4-m spectrophotometric comparison of discrete HII regions and diffuse ionized gas (DIG) in M31. We have sampled the NE half of M31 with most data for the 10kpc spiral arm which shows evidence for a high star-formation rate. The spectral coverage from 3500 to 7000\rmÅallows for the comparison of emission line fluxes of [OII], [OIII], [NII], and [SII] relative to the hydrogen Balmer lines. Several types of HII regions were observed, including bright classical nebulae, large diffuse nebulae and ring-like HII regions. The emission line characteristics of these types of nebulae all appear to vary smoothly with emission measure extending down to the very faint DIG which permeates the entire disk. We have also looked for abundance affects on the emission line ratios in the nebulae and the DIG as a function of radial position in the galaxy. Diagnostic diagrams are used to analyze the properties of the ionizing flux in the different HII regions and in the DIG.
