4. Hydrostatic equilibrium model
We interpret the low-intensity profile wings at the extreme
velocities as emission from neutral gas in hydrostatic equilibrium
with the gravitational potential of the Galaxy. The density
distribution of the H I
halo gas is then due to the balance between the turbulent pressure of
the HVD component and the gravitational potential
We model the distribution of the halo gas throughout the Galaxy following the approach of Taylor & Cordes (1993), separating radial and horizontal dependencies: where is the mid-plane density and defines the radial density distribution; = 8.5 kpc.
We modeled the emission of H I halo gas corresponding to such a distribution for various scale lengths and , assuming that the halo gas is co-rotating with the disk. The rotation curve was taken from Fich et al. (1990). The best fit to the observations is given in Fig. 1 for the scale lengths kpc and = 15 kpc. This result yields a value of c =3, implying a halo model where gas, magnetic fields and cosmic rays are in pressure equilibrium. Fig. 4 shows the corresponding distribution .
© European Southern Observatory (ESO) 1998
Online publication: March 30, 1998