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Session 17 - ISM, Star Formation & Planets.
Oral session, Monday, June 09
North Main Hall C/D,

[17.02] First Results from the WHAM Spectrometer: H\alpha Emission from HVCs and the First Detection of He I \lambda5876 from the WIM

S. L. Tufte (U. Wisconsin, Madison)

The Wisconsin H-Alpha Mapper (WHAM) is a unique new instrument for the detection of faint optical emission lines from diffuse ionized gas in the disk and halo of the Galaxy. WHAM consists of a 15 cm aperture, dual-etalon Fabry-Perot spectrometer coupled to a 0.6 m siderostat. Its primary purpose is to conduct a sensitive kinematic survey of the northern sky (\delta > -30\arcdeg) in the H\alpha line from Kitt Peak with 1\arcdeg\ spatial resolution and 12 km s^-1 spectral resolution. This survey, which is well under way (over 10,000 spectra have been measured), will provide the first detailed information about the warm ionized medium (WIM), a recently recognized major component of the interstellar medium.

The first observations using the WHAM spectrometer include a study of emission lines from high velocity clouds in the M, A, and C complexes, with most of the observations on the M I cloud. I present results that include clear detections of H\alpha emission from all three complexes. The intensities range from 0.06 R to 0.20 R.

Another study obtained the first detections of the He I \lambda5876 recombination line from the WIM. This line has been detected in four directions in the Galactic plane. The intensity ratios of the \lambda5876 line to H\alpha, while somewhat higher than the ``upper limit'' originally published by Reynolds amp; Tufte (1995), indicate that the spectrum of the radiation ionizing the WIM is significantly softer than that emitted by the O stars in the solar neighborhood.

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Program listing for Monday