Photoionized gas in hydrostatic equilibrium: The role of gravity

Abstract

We present a method to include the effects of gravity in the plasma physics code CLOUDY. More precisely, a term is added to the desired gas pressure in order to enforce hydrostatic equilibrium, accounting for both the self-gravity of the gas and the presence of an optional external potential. As a test case, a plane-parallel model of the vertical structure of the Milky Way disc near the solar neighbourhood is considered. It is shown that the gravitational force determines the scaleheight of the disc, and it plays a critical role in setting its overall chemical composition. However, other variables, such as the shape of incident continuum and the intensity of the Galactic magnetic field, strongly affect the predicted structure. © 2010 The Authors. Journal compilation. © 2010 RAS.