Session 7 - Gas and Dust in the ISM.
Display session, Monday, June 10
Great Hall,

## [7.04] Correlation between Hydrogen-alpha and 100-micron Emissions

P. R. McCullough (Univ. of Illinois)

Observations of diffuse H\alpha emission in a \sim12 degree field at Galactic latitude --65 degrees show a correlation with infrared cirrus previously observed by IRAS. Anisoptropy of the H\alpha surface brightness is typically 0.2 Rayleighs (i.e. emission measure \sim0.5 cm^-6-pc) on angular scales of 0.1-1.0 degrees. Significantly for further observations of this type, sensitivity appears to be limited by confusion of real structures in the ISM, rather than by telluric sky brightness. The H\alpha emission associated with infrared cirrus likely is due to a combination of emission from gas at high latitude and emission from Galactic H II regions that has been backscattered by dust at high latitude. Observations of this type may provide a means to distinguish between Galactic foreground and cosmic background for both the free-free emission and the thermal dust emission associated with the warm ionized medium of the Milky Way.