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B. Otte (Johns Hopkins University)
Diffuse ionized gas (DIG) is a poorly understood component of galaxies that can be seen extending well beyond the stellar disks of edge-on spirals. I will discuss the temperature of the extraplanar DIG derived from the analysis of longslit spectra of a small sample of nearly edge-on spiral galaxies. A rise in electron temperature with increasing distance from the midplane could explain the observed increases in the optical emission line ratios. Our spectra include the major nebular emission lines from [OII] at 3727\,Å\ to [SII] at 6716.4\,Å. The [OII] doublet is a good tracer of temperature variations due to its high excitation energy. The combination of the observed emission lines allowed us to derive electron temperatures, abundances, and ionization fractions for our sample galaxies. The most reasonable values for these properties were obtained when the oxygen abundance was held constant along the slit. In this method, the electron temperature tended to increase towards the halo in most galaxies of our sample. In slits parallel to the midplane of the galaxies, the electron temperature increased with decreasing emission line intensity, suggesting that variations in temperature are more generally correlated with variations in gas density. This behavior helps to identify the heating mechanisms that could be responsible for the temperature increase with increasing distance from the midplane.