Astron. Astrophys. 342, 213-232 (1999)
We compared selected fields from the
keV ROSAT all-sky survey
against the Leiden/Dwingeloo H I survey looking for
correlations between HVCs and soft X-ray emission. We considered the
soft X-ray radiation transfer in detail towards several prominent HVC
complexes. Our results show that:
The observed SXRB shows a smooth diffuse X-ray source intensity
distribution at the higher latitudes (see Fig. 7).
Small- and large-scale
variations of the observed SXRB distribution can be attributed to
H I alone traces the amount of soft X-ray
absorbing interstellar matter well.
Warm H I (i.e. the intercloud medium) traces most
of the soft X-ray absorbing interstellar medium.
The intensity of the distant X-ray emission decreases with
increasing angular distance to the galactic center, implying that most
of the distant soft X-ray emission is galactic in origin. The distant
SXRB shows comparable intensities on the northern and southern
The distant soft X-ray emission probably consists of a
superposition of a galactic X-ray plasma component
and a component of unresolved
extragalactic point sources. More than 50% of the total radiation
observed towards the galactic anticenter can be attributed to the
galactic halo plasma emission.
The above results are consistent with those of Pietz et al. (1998a;
We detected the following deviations from the smooth distant
galactic X-ray background intensity distribution towards several
prominent HVC complexes:
Large portions of HVC complex C are positionally associated with
excess soft X-ray emission.
Towards a part of HVC complex D, we detected enhanced soft X-ray
emission, positionally associated with an HVC filament. However, we
note that there is also an IVC close to this area of excess
We detected enhanced soft X-ray emission in the direction of
Mrk 509, where Sembach et al. (1995) found highly-ionized gas
associated with HVC complex GCN.
Towards complex WA we found inconclusive evidence for excess
© European Southern Observatory (ESO) 1999
Online publication: December 22, 1998