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R. J. Pifer, S. L. Tufte, R. J. Reynolds, L. M. Haffner (Astronomy Department, Univ. of Wisconsin, Madison)
The sightline toward the O9.5 star HD93521, located 1.5 kpc above the Galactic plane at l = 183\rm o, b = +62\rm o, has been investigated in great detail by Spitzer & Fitzpatrick using absorption lines seen in HST GHRS spectra. These authors came to the controversial conclusion that the data could only be explained by assuming that the gas in the halo was partially ionized. McKee & Slavin have proposed a different model in which partial ionization is avoided by assuming that the clouds are composed of many cloudlets with a sufficiently porous spatial structure for ionizing photons to reach the inner cloudlet surfaces. In order to obtain additional insight (and add additional constraints) to the story unfolding for this sightline, the Wisconsin H-Alpha Mapper (WHAM) has observed this direction in two forbidden emission lines: [S~II] \lambda6716 and [N~II] \lambda6584. These spectra will be presented and compared to the WHAM H\alpha spectra for this sightline (see the adjacent paper by Hausen et al.). In the near future, we will combine these {\em emission} line measurements with the {\em absorption} line data of Spitzer & Fitzpatrick to further explore the physical state of the ionized gas in the halo, paying particular attention to the question of partially ionized clouds.
This work is supported by a grant from the National Science Foundation (AST 9619424) and by the University of Wisconsin Undergraduate Honors Program.
If the author provided an email address or URL for general inquiries, it is a
s follows:
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