Broadening of spectral lines due to dynamic multiple scattering and the Tully-Fisher relation

The frequency shift of spectral lines is most often explained by the Dopple r effect in terms of relative motion, whereas the Doppler broadening of a p articular line mainly depends on the absolute temperature. The Wolf effect, on the other hand, deals with the correlation-induced spectral change and explains both the broadening and shift of the spectral lines. In this frame work a relation between the width of the spectral line is related to the re dshift z for the line and hence with the distance. For smaller values of z a relation similar to the Tully-Fisher relation can be obtained and for lar ger values of z a more general relation cah be constructed. The derivation of this kind of relation based on dynamic multiple-scattering theory may pl ay a significant role in explaining the overall spectra of quasistellar obj ects. We emphasize that this mechanism is not applicable for nearby galaxie s, z less than or equal to 1.