HI IN THE GALACTIC HALO

We find solid evidence for diffuse HI gas at substantial z heights in our Galaxy, with a velocity dispersion of sigma = 60 km s(-1) and a ve rtical projected column density of N-Hi = 1.4 . 10(19) cm(-2). This pe rvasive component of the emission spectrum could be identified in the Leiden/Dwingeloo 21-cm Survey (LDS) after increasing the accuracy furt her by correcting the observations for reflections from the ground. In vestigations of receiver bandpass and stray radiation effects could no t explain this component as an artifact of the instrumentation. Assumi ng that the distribution of mass and pressure perpendicular to the gal actic plane is in hydrostatic equilibrium with the galactic potential, we derive a vertical exponential scale height of h(z) similar or equa l to 4.4 kpc for the observed diffuse high-dispersion HI component. Th e radial distribution is characterized by the corresponding galactocen tric scale length A(1) similar or equal to 15 kpc.