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Session 43 - The Diffuse ISM: Milky Way and Beyond.
Display session, Tuesday, June 11
Utilizing a large-aperture, double-etalon Fabry-Perot and modern CCD technology, the Wisconsin H-Alpha Mapper (WHAM) attains unprecedented sensitivity at 10 km s^-1 resolution for faint emission line studies. Starting this fall, WHAM will begin mapping the northern sky in H\alpha from Kitt Peak. We present two sets of data on ionized gas in our Galaxy taken during the instrument's testing and development phase at Pine Bluff Observatory in Wisconsin.
First, we discuss a sensitive search for an [O \sc iii] \lambda5007 counterpart to the high-latitude O \sc iii] \lambda1663 emission detected by Martin amp; Bowyer (1990, ApJ, 350, 242). In directions where they find evidence for O \sc iii] \lambda1663 emission, simple, single-temperature (T \sim 10^5 K) gas calculations suggest I_5007 \sim 0.1--0.2 R. A complex multi-temperature model such as turbulent mixing layers predicts I_5007 to be 3--30 times greater. With these predictions in mind, we discuss our new Fabry-Perot observations of [O \sc iii] \lambda5007.
Second, we discuss a search for H\alpha emission from high-velocity clouds in the vicinity of Mrk 509. Sembach et al. (1995, ApJ, 451, 616) report the discovery of a highly ionized component of these clouds seen through UV absorption lines toward Mrk 509. An intensity gradient in high velocity H \sc i 21 cm emission near the line of sight suggests a cloud boundary or transition region. We compare our new observations in H\alpha to H \sc i measurements in the region to determine the spatial ionization characteristics of these clouds in light of the highly ionized gas present toward Mrk 509.
This work has been supported by the National Science Foundation.
Program listing for Tuesday