Multiwavelength analysis of the radio source 3C111 through VLBA observations

This thesis will present the results of the analysis of multi-wavelength observations of the active galaxy 3C111, obtained with the Very Long Baseline Array (VLBA). The observations were made at 5, 8.5, 15, 21, 43, and 86 GHz. Radio emission from active galaxies (AGNs) is one of the most interesting and information-rich phenomena among those accessible using the VLBI technique. AGNs are excellent laboratories for a variety of extreme physical processes. The standard model of AGNs suggests the presence of a supermassive black hole (SMBH) at the center of the galaxy, which accretes matter and is surrounded by obscuring torus. The complex dynamics around the SMBH and the presence of intense magnetic fields, may lead to the production of two plasma streams of charged particles, emitting synchrotron radiation, called jets with opposite orientation to each other. Given its proximity, 3C111 is an excellent object to study the physics of jets with mm-VLBI.The data gathered with the VLBA are calibrated, yielding source images with the highest resolution possible for this 86 GHz array. In addition to the total intensity images, polarization maps are also calculated for all bands. By comparing the total intensity images, spectral index maps can be calculated for all adjacent frequency pairs. Moreover, for some triplets of frequencies it is also possible to compute rotation measure (RM) maps. In order to provide relationships between distinct features in the jet, the spatial distribution of the emission in each band is modeled with a set of circular Gaussian components. For each of them, it is provided an estimate of the brightness temperature and the magnetic field. For each of the physical quantities found during the model fitting of the components, a relation is provided that is more or less accurate, depending on the parameters considered.