Session 50 - Interstellar Medium I.
Display session, Thursday, January 08
Exhibit Hall,

## [50.01] A ROSAT X-Ray Background Survey in the Galactic Plane

J. N. Bregman (U. Michigan), P. M. Knezek (Johns Hopkins U.), S. L. Snowden (GSFC), A. K. D'Onofrio (U. Michigan)

A close relationship is expected between the volume occupied by hot gas and its displacement of cold gas, which should be reflected in the structure of the HI and X-ray intensity maps. To investigate this relationship, we have used the ROSAT PSPC to obtain energy-dependent X-ray intensity maps of the region 214.4 > l > 208.4, -3.7 < b < 3.7. This required a series of 40 overlapping pointings, resulting in an average exposure time for the map of 3.9 ksec, more than an order of magnitude deeper than the maps of this region from the ROSAT All Sky Survey (0.36 ksec). Point sources can be identified easily and statistically meaningful maps can be constructed on the same angular resolution as the HI survey of this region (20^\prime). This analysis will focus on the X-ray emission in a soft band (0.14-0.284 keV) and a harder band (0.44-2.0 keV). There is a general anticorrelation between the X-ray emission (soft and hard band) and the integrated HI intensity as a function of latitude, averaged over longitude. There is a local X-ray brightening upon crossing the midplane, which is partly resolved into point sources in the hard band. Some specific correlations between X-ray intensity in the hard band and HI structure is evident, and the implications for this are discussed.