AAS Meeting #193 - Austin, Texas, January 1999
Session 83. Interstellar Medium
Oral, Friday, January 8, 1999, 10:00-11:30am, Room 9(C)

## [83.04D] The Three-Dimensional Structure of the Hot Interstellar Medium

C. E. Grant, D. N. Burrows (Penn State University)

The diffuse soft X-ray background is primarily of Galactic origin. Million degree gas in both the Local Hot Bubble and the Galactic halo produce the 1/4-keV band emission, while a combination of extragalactic and galactic point sources, and diffuse emission appear to produce the 3/4-keV band emission. While energy-dependent intensity maps provide a wealth of information about the two-dimensional structure of the X-ray emitting material, constraining the distance to the emission is vital towards full understanding of its three-dimensional structure. X-ray shadows provide a means to differentiate foreground and background emitting regions towards absorbing clouds. I present analysis of ROSAT PSPC observations towards ten molecular clouds at a range of Galactic latitudes and distances. Spatial anti-correlation between infrared 100 \mum dust emission, a tracer of the absorbing gas, and the X-ray emission is studied by fitting a single-slab absorption model. The nearest of the clouds are used to confirm the scaling of the Local Hot Bubble presented by Snowden et al. (1998, ApJ, 493, 715). The 1/4-keV band observations towards clouds at high Galactic latitude confirm the patchy structure of the hot Galactic halo. The 3/4-keV band observations help define the spatial structure of the hotter emission and thus its possible source(s).