Modelling the spectral energy distribution and polarisation of blazars

Abstract

The optical emission from most blazars is dominated by the polarised synchrotron radiation of relativistic electrons in the jet. However, the thermal radiation from the accretion disc and host galaxy also contributes towards the high and low frequency ends of the optical spectrum. As the accretion disc and host galaxy emissions are expected to be unpolarised, they may manifest as a decrease of the degree of polarisation towards the high- and low frequency ends of the optical spectrum, respectively. This motivates a target of opportunity (ToO) programme for spectropolarimetry observations of gamma-ray blazars with the Southern African Large Telescope (SALT). A model is constructed that combines modelling of the spectral energy distribution (SED) and of the degree of optical polarisation to constrain the accretion disc contributions in the spectra of blazars. This dissertation presents a simultaneous SED and polarisation model fit to the Flat Spectrum Radio Quasar (FSRQ) 4C+01.02 in its are and quiescent states. With this model, the electron distribution energies γ1, γb and γc, electron spectral indices, ordering of the magnetic field of the jet, accretion disc luminosity and the mass of the black hole ∼ 4.0 × 108 M