G. Ferland, R. Williams, R. Porter, and P. van Hoof. [[We also thank the referee, W. Henney, for his insightful comments and suggestions, leading to major improvements in our Milky Way model.]{}]{} Financial support for this work has been provided by the Spanish *Ministerio de Educación y Ciencia* through project AYA2007-67965-C03-03.

User Guide {#secUserGuide}
==========

In order to specify a hydrostatic equilibrium configuration, the [[constant pressure]{}]{} command must be included in the [Cloudy]{} input script. In addition, a [[gravity]{}]{} command with syntax

     gravity <symmetry> [<factor> [_log]]

has been implemented. The compulsory argument [[symmetry]{}]{} must be either *spherical* or *plane-parallel* in order to tell the code whether to use equation (\[eqGrav\_sphere\]) or (\[eqGrav\_plane\]) to compute the gravitational acceleration[^6]. An optional factor can be introduced that multiplies the gas mass, mimicking the presence of an external component with identical distribution. A more flexible way to specify an external potential is provided by the command

     gravity external <mass> [<extent> <index>] [_log]

that models a distribution of mass around the centre of symmetry of the system. In the spherical case, the first number represents the mass (in solar masses) of a pointlike object located at $r=0$; in the plane-parallel case, it corresponds to the 