  Combined Poisson's-Boltzman equations of hydrostatic equilibrium were set up
and solved numerically for different baryonic components to obtain the
molecular scale height as defined by the Half Width at Half Maxima (HWHM) in
the spiral galaxy NGC 7331. The scale height of the molecular gas was found to
vary between $\sim 100-200$ pc depending on the radius and assumed velocity
dispersion. The solutions of the hydrostatic equation and the observed rotation
curve were used to produce a dynamical model and consequently a simulated
column density map of the molecular disk. The modelled molecular disk found to
match with the observed one reasonably well except at the outer disk regions.
The molecular disk of NGC 7331 was projected to an inclination of 90$^o$ to
estimate its observable edge-on thickness (HWHM), which was found to be $\sim
500$ pc. With an HWHM of $\sim 500$ pc, the observed edge-on extent of the
molecular disk was seen to be $\sim$ 1 kpc from the mid-plane. This indicates
that in a typical galaxy, hydrostatic equilibrium, in fact, can produce a few
kilo-parsec thick observable molecular disk which was thought to be difficult
to explain earlier.

Astrophysics of Galaxies