ABSTRACT

A theoretical scheme is developed for computing line profiles from optically thin rotating and expanding disks and systems of emission line clouds moving radially inside cones. The models include turbulent motions, atmospheric seeing and effects induced by the size of the observing aperture. As an example, the asymmetric extranuclear Ha line profiles along the major axis of NGC 7469 are fitted by a rotating disk model.

INTRODUCTION

Disks and cones are basic geometries for systems of emission line clouds in active galaxies. Many lines, as e.g. forbidden emission lines, are formed in optically thin clouds so that the line profiles only depend on the geometrical and kinematical distribution of the clouds and radiative transfer effects can be neglected. Hence, infinitesimally spatially resolved profiles are calculated by integrating along that part of the line-of-sight that intersects the configuration. Those volume elements whose line-of-sight velocity component equals v contribute to the intensity I(v).

For systems following radial power laws for both velocity and emissivity we derived analytical expressions for the profile functions. These results are used to check the pure numerical code whose working method is based on collecting and summing up all emissivities falling in a given velocity bin along the considered line-of-sight. Additional isotropic turbulent motions are taken into account by convolving the profiles with a normalized Gaussian of a given σ. The line-of-sight profiles are stored in a data cube (x, y, v). Spatial convolutions to mimick the effects of atmospheric seeing and finite observing apertur and pixel sizes are simply carried out with the ESO image processing system MIDAS.