Speaker
Description
Blazars are a subclass of Active Galactic Nuclei (AGN) that contain relativistic jets oriented towards the observer. The Spectral Energy Distribution (SED) of these sources are typically dominated by two broad non-thermal components. The lower-energy component is produced by synchrotron emission from relativistic electrons in the jet, while the high-energy component can be a combination of inverse Compton scattering and hadronic processes. Certain blazars contain an additional underlying thermal component at optical/ultraviolet wavelengths that can be difficult to disentangle from the non-thermal emission. Despite the current knowledge of these sources, several aspects are not fully understood, including the underlying magnetic field geometry, particle acceleration mechanisms, and the exact contributions of different emission processes. In addition to multi-wavelength observations, polarization measurements of these sources can provide critical insights to constrain some of their properties. In this study, we present results from the Spectro-Polarimetric Observations of TeV Sources (SPOTS) campaign. The results include optical spectro-polarimetric observations of 14 TeV-emitting blazars using the Southern African Large Telescope (SALT). Overall, observations of the sample during this campaign showed a low average optical polarization (Π<10%). A few sources exhibited smooth angle rotations on time scales of days to weeks, while most others showed stochastic variations consistent with turbulent magnetic fields. The average ordering of the magnetic field was modelled for each source and found to be generally low, consistent with emission arising in extended, turbulent regions of the jet. For individual sources, correlations between polarization and its frequency dependence were found. The nature of the frequency dependence varied across observations, indicating that simple one-zone models are insufficient to describe the sources and that FB must be wavelength-dependent. The future of the study will combine the polarization measurements with multi-wavelength data in order to model the SEDs of these sources.