A dust scattering model of M82

Abstract

This thesis contains an investigation into polarisation produced by light scattered within nebulae and galaxies. In the first chapter a general outline of mechanisms, producing polarisation is given. This is followed in chapter two by a detailed analysis of the theory of scattering. Here we show the formulation of the theory for scattering from small particles (Raylei^ scattering) and scattering from larger particles, (Mie theory). Chapter three gives an overview of interstellar grains, their composition, growth, destruction, size distributions and the possible sources of their origins. This is followed in the next chapter by a study of the galaxy m82. Here is given the scientific development of the galaxy showing previous models developed and the controversy which has built up over the years on whether the galaxy actually exploded or not. Chapter five contains a dust scattering model of the galaxy. This is based upon the hypothesis that the galaxy has drifted into an enormous intergalactic dust cloud. The results and consequences of the model are presented in chapter six. The dust scattering model used for M82 assumed Rayleigh scatterers. Chapter seven shows the results from model nebulae consisting of Mie particles. Here discussion is given to the effect on the predicted results when varying the properties of the grains. We also mention the potentials of other forms of polarisation techniques.