General relativistic radiative transfer
In this thesis I explore the radiative transfer process where relativistic effects are important. Strong gravity modifies the observable properties of the light emitted by an object. A photon no longer travels in straight lines, and its frequency is shifted as it propagates. Gravitational lensing may make multiple images of the emitter, further modifying the temporal and spectral properties of its emission. The first part of my thesis investigates the motion of particles in a strong gravitational field (near a black hole). I derive the equations of motion for massive or massless particles acted upon by external forces. Efforts are made to work out self-consistently the structure of the accreting flow around central super-massive black holes in active galactic nuclei (AGN). I calculate the line and continuum emission from accretion disks and tori around rotating black holes using a ray-tracing method. I also study the effect of line-of-sight absorption, with a model in which the absorbing medium is composed of virialised clouds. The second part of the thesis examines situations where scattering is important. I derive a covariant transfer formulation which uses a basis set of projected symmetric tensors for a series of moments. My formulation is similar, yet simpler than an alternative method which uses projected symmetric trace-free tensors derived by Thorne (1981). I then calculate the emission from accretion tori where electron scattering dominates other radiative processes.