A distribution function calculation of the H profiles of high-velocity shocks -- III. Profiles from varying angles of observation

Abstract

Steady-state Hα profiles from strong non-radiative shocks have been investigated in terms of the velocity distribution of the neutral gas by Lim & Raga. The authors' use of a one-dimensional distribution function, which describes only the neutral velocities in the direction normal to the plane of the shock front, limits the predicted line profiles to the line of sight in the direction of the flow. The steady-state model is here extended to a multidimensional distribution function which follows the thermalization of the atomic hydrogen in three dimensions. From this velocity structure it is possible to calculate the steady-state Hα emission profile seen by an observer with an arbitrary line-of-sight orientation to the shock velocity vector. The ionic shock structures used in the kinetic calculation are still of a plane-parallel nature. The predicted Hα profiles from the higher dimensional model follow the same trend of decreasing broad-to-narrow component ratio with increasing shock speed as those of the plane-parallel model. The effect of a variation of the line-of-sight angle from the normal is to reduce the velocity shift between the broad and narrow components in the line profile. Rotation around the shock normal has no effect upon the observed emission profile, as would be expected for a planar shock front.