Hidden Dust in Blazars

Blazars are extremely bright sources in the sky, typically so far away that we can only seethem as point like sources. They are a type of active galactic nuclei (AGN), where a jet ofrelativistically moving plasma is pointed directly towards us. The extreme brightness ofthe blazars is often explained by very strong beaming due to the fast moving plasma andinverse Compton scattering of a seed photon field. The nature of this seed photon fieldis still under research. Different models including scattering of other emissions from thejet or from the AGN core are suggested. Recently, detections from AP Librae supportingthe emissions from a circumnuclear disc – a ∼ 100 parsec structure around the AGN –were made with the Atacama Large Millimeter/Submillimeter Array (ALMA). This master’s thesis is based on the research and activities conducted during myinternship at Mets¨ahovi Radio Observatory. During the internship I investigate the ALMAdata for two similar targets, Ton 599 and TXS 0506+056, but found no conclusive evidenceof a circumnuclear disc in either of them.