Thalia Traianou

PhD Project: High-angular resolution structural and polarimetric variability of the γ-ray blazars TXS 2013+370 and 3C 454.3 

PhD Supervisor: Dr. Thomas Krichbaum

Collaborators: Dr. B. Boccardi, Dr. E. Angelakis, Dr. C. Casadio, Prof. Dr. E. Ros, Dr. I. Agudo, Prof. Dr. A.P. Marscher, Prof. Dr. J.A. Zensus

The PhD Project: VLBI is a technique that allows us to image distant astrophysical systems at the highest possible angular resolutions. Thus, probing smallest physical scales  providing insight about the physical causes of AGN activity, the formation and acceleration of AGN jets, the origin of gamma-ray emission and so forth. My PhD focuses chiefly on the structural evolution and polarization variability of TXS 2013+370 and 3C 454.3 blazars using VLBI imaging at the ultra-high angular resolution. VLBI imaging at 7 mm and 3 mm offers a more direct view into the AGN core regions in the vicinity of the super massive black hole, which are inaccessible at longer wavelengths due to synchrotron self-absorption. Current jet models assume that, at these scales, the ultra-relativistic outflows are formed and accelerated through electromagnetic forces.

By combining spectral turnover frequency data with flux density and size measurements from VLBI I am investigating the regimes in which jets are magnetic or kinetically dominated. Furthermore, I intend to perform a spectral decomposition of the inner jet region as a means of discriminating between synchrotron self-absorbed jet components and stationary features at the jet base. The latter are expected to be formed through jet recollimation in an over-pressured jet nozzle and to be, possibly, responsible for gamma-ray production. Moreover, polarization of radio emission in extragalactic jets at such high angular resolution can carry important information about the magnetic field structure in the innermost regions of the jets. I will use polarization imaging of the aforementioned blazars to distinguish between different possible magnetic field configurations. Flux variations of the core and jet polarization are often accompanied by near in time variations of the gamma-ray flux and possibly the optical polarization. Another goal of my PhD is  therefore multi-wavelength polarimetric imaging in order to reveal the magnetic field topology.

About me: I come from a small village in the region of Florina, Greece. Since my childhood, I have been fascinated by the universe, thus I decided very early on that I want to broaden my knowledge and be involved actively in this scientific field. I studied physics at the Aristotle University of Thessaloniki. For my diploma thesis I conducted a photometric study of a selected sample of AGN - galaxy pairs, in order to detect evidences of physical interactions between the two. As evidences were taken the star formation between them and the class misidentification. I started my PhD at the VLBI group of the MPIfR at the end of 2016 and I completed it in mid 2020.

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