Roberto Angioni (2015-18)

PhD Project: VLBI and gamma-ray studies of radio galaxies in the TANAMI monitoring program

Successfully (magna cum laude) defended on October 19, 2018

PhD Supervisors: Prof. Dr. Eduardo Ros & Prof. Dr. Matthias Kadler

Collaborators: Prof. Dr. E. Ros, Prof. Dr. M. Kadler, Dr. R. Ojha, Dr. C. Mueller, Dr. F. Krauss, Prof. Dr. J.A. Zensus, TANAMI collaboration, Fermi-LAT collaboration

The Project  My PhD has taken place in the framework of the TANAMI and Fermi-LAT collaborations, and involves different interconnected projects.

The first one is a sample study of the radio galaxies in the TANAMI monitoring program of radio-loud AGN in the southern hemisphere. I am performing VLBI imaging at 8.4 GHz and 22 GHz, spectral index mapping, and jet kinematic analyses from the multi-epoch observations. The outcome will be a sample paper which will provide unprecedented information on noteworthy southern sources which have never been studied with this detail at milliasrcsecond resolution.

I am also interested in the multi-wavelength properties of radio galaxies, particularly in the gamma-ray band, where they have been revealed by the Fermi-LAT telescope as a new elusive but fascinating class of sources. Although they make up only about 1-2% of all sources observed by Fermi, radio galaxies offer a complementary view of relativistic jets w.r.t. blazars, which are the dominant population in the gamma-ray sky. This striking difference is due to the different jet orientation: blazars have relativistic jets closely aligned with our line of sight, so their emission is strongly Doppler boosted, and they are much brighter and therefore easier to detect in gamma-rays. Radio galaxies are the misaligned counterpart of blazars. They allow us to test the orientation based unified models, the generality of particle acceleration and emission models (which are usually developed for blazars), and they provide the only detection of gamma-ray emission from diffuse structures in radio-loud AGN at the moment.

Finally, I am also interested in gamma-ray faint sources in large radio samples. There is a well established connection between radio and gamma-ray emission in AGN. Nonetheless, there are several bright radio-loud sources which still lack a gamma-ray detection. This is true for the TANAMI sample as well, where 28% of the sources are not detected by Fermi-LAT. I am analyzing LAT data using the recently developed Pass8 analysis software, in order to obtain a detection for these sources or more stringent upper limits on their high-energy emission. I am also looking at their broad band Spectral Energy Distribution (SED), to see if their lack of a gamma-ray detection may be due to the lower SED synchrotron peak w.r.t. LAT-detected sources.

About me  I come from a small village in the region of Sardinia, Italy. I attended a scientific high school, then moved on to obtain a BSc in physics at the University of Cagliari, where I had my first short approach with research in astronomy with a thesis on water maser emission in an AGN, which I discussed in September 2012. Having realized that I wanted to continue in the field, I chose to continue my studies at the University of Bologna, where I obtained my MSc in Astrophysics and Cosmology with a thesis work of ~1 year on gamma-ray emitting radio galaxies in the Fermi and TeV band, with prospects for the next TeV facility, the Cherenkov Telescope Array. I obtained my degree in July 2015, then moved on to my current PhD position in the IMPRS, working in the VLBI group of the MPIfR starting from September 2015.

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