An investigation of the active galaxies M82 and NGC 5128

Abstract

In this thesis we present multi-waveband imaging polarimetry and spectropolarime- try of the starburst galaxy M82 and multi-waveband imaging polarimetry of the active galaxy NGC 5128. A review of previous studies of these galaxies is given. The imaging polarimetry of M82 in broadband filters reveals a polarization pattern that is due to scattering of light from the galactic disk and a nuclear starburst component. The Hq filter polarimetry shows a centrosymmetric pattern from the nuclear component only. The spectropolarimetry of the southern filaments of M82 shows evidence for a mixture of scattering and intrinsic emission from the walls of a superwind blown cavity. Only the Hɑ systemic component of M82 is seen in polarized intensity, the blueshifted component is due to intrinsic emission only. NGC 5128 displays a polarization pattern in its dust lane which is produced by extinction due to aligned non-spherical dust grains in a magnetic field. The wavelength dependence of the polarization in the dust lane is found to follow a Serkowski curve in the central regions.