PhD Supervisor: Emmanouil Angelakis
Collaborators: Dr. L. Fuhrmann, V. Karamanavis, Dr. A. Kraus, Prof. Dr. V. Pavlidou, Prof. Dr. J.A. Zensus
Date: August 29, 2014
My project My research is focused on the investigation of the microphysics of AGN jet plasma emission elements, i.e. Synchrotron-emitting populations described by a single energy distribution in the presence of a local magnetic field topology.
The Synchrotron theory predicts polarized emission whose characteristics depend on the optical depth of the emitting material and the magnetic field uniformity. The transition between optically thick and thin states, uniquely observed in radio bands, is expected to be correlated with the measured polarization degree, and is associated with polarization angle rotations of 90° and reversal of the Circular polarization handedness (Pacholczyk 1977). Furthermore, theoretical predictions for the radiative transfer coefficients suggest a connection between the Linear and Circular polarization characteristics and the emitting plasma state (e.g., cold or ultra-relativistic, Huang et al. 2011) and composition (i.e., e-/e+ or e-/p+ jet, Wardle et al. 1998). The recent discovery of optical polarization angle rotations associated with high-energy flares, on the other hand, provides an independent and complementary approach to the problem (Marscher et al. 2008).
The importance of high-cadence, multi-frequency polarization monitoring in the pursuit of these answers is invaluable. The F-GAMMA and RoboPol programs have resulted unique databases in the radio and optical bands respectively, for such studies. The ongoing analysis of the F-GAMMA dataset that recovers Linear and Circular modes, shows that the polarization parameters (degree, angle and handedness) follow exactly the predicted behavior; bringing the extragalactic plasma of vast cosmological distance to the observers “lab” allowing the construction of a self-complete “toy” model for further analysis and detailed parameter study (Fig.1). In the process, sources of significant and stable Circular polarization characteristics to be used as standards, have been identified (Myserlis et al. 2014). RoboPol data analysis has revealed that the gamma-ray--loud and gamma-ray--quiet sources have different optical polarization properties (Pavlidou et al 2014).
This project accesses the micro-physics of AGN jets at the smallest possible scales i.e. the plasma emission elements. It aims at enriching our current understanding particularly of their particle composition, magnetic field uniformity and plasma states as well as the very details of the emission mechanism; and for the first time through the complete picture drawn by both Linear and Circular polarization behavior in combination with optical thickness evolution.
About me I received my Physics degree from the Aristotle University of Thessaloniki, Greece, where I was also born. Afterwards, started my Doctoral Degree as member of the IMPRS for Astronomy and Astrophysics at the VLBI group of the MPIfR. After the completion of my PhD, I am eager to follow a career path in academia in the international and inspiring environment of a Research Institute like MPIfR or at a University.