Emission from the Local Galactic Halo in the 1/4 keV Band
Session 12 -- Interstellar medium
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

## [12.16] Emission from the Local Galactic Halo in the 1/4 keV Band

M. Juda (SAO)

Pointed observations with the ROSAT PSPC toward clouds at high galactic latitude provide a unique opportunity to probe emission from the local galactic halo in the 1/4 keV band. I present data from five fields toward clouds at $|b|~>~60^\circ$ identified through their IRAS 100~$\mu$m emission, two in the north galactic hemisphere and three in the south. In four of the five fields significant shadows are detected (2 north, 2 south). The derivation of the brightness of the shadowed component depends strongly on the assumed location and amount of absorbing material. Scaling the IRAS 100~$\mu$m emission by 10$^{20}$~H~atom~cm$^{-2}$/MJy~sr$^{-1}$ and correcting for the difference from the observed average 21~cm derived column density, the implied brightness of the distant emitting component is the same for the two northern latitude fields at $\rm{\sim1.2\times10^{-3}~counts~s^{-1}~arcmin^{-2}}$; this brightness is lower than that seen in the direction of Draco (Burrows \& Mendenhall 1991, Snowden et al. 1991) and higher than in Ursa Major (Snowden et al. 1994). The two southern fields also have the same derived distant brightness at nearly the same level as the northern fields, $\rm{\sim1.0\times10^{-3}~counts~s^{-1}~arcmin^{-2}}$. Approximately 20\% of this emission may be attributed to an extragalactic background (Hasinger et al. 1993). The remaining emission, $\rm{\sim0.8\times10^{-3}~counts~s^{-1}~arcmin^{-2}}$, would be provided by the local galactic halo. If these x-rays arise from a collisionally excited plasma at a temperature of $10^6$~K the required emission measure is $\rm{\sim0.0033~cm^{-6}~pc}$.

\bigskip \noindent Burrows \& Mendenhall 1991, Nature, 351, 629.\\ \noindent Hasinger et al. 1993, A\&A, 275, 1.\\ \noindent Snowden et al. 1991, Science, 252, 1529.\\ \noindent Snowden et al. 1994, ApJ, 430, 601.