Promotionskolloquium
Petra Benke	SCHEDULED

MPIfR

Active galactic nuclei (AGN) jets are the most luminous and energetic objects in the Universe, with many open questions regarding their formation, evolution and variability. In this talk, we will take a closer and closer look into the parsec-scale structure of these objects, using very-long-baseline interferometry (VLBI). I show first-light images from the 2.3 GHz monitoring of the TANAMI program, the only VLBI monitoring targeting southern-sky AGN. The 2.3 GHz monitoring was established to provide quasi-simultaneous data of the parsec-scale jets for the Fermi LAT, which lacks the resolution to probe the central region of AGN. I will then discuss a multiwavelength study of a gamma-ray flaring blazar and a radio multi-frequency observation of a nearby radio galaxy. Both of these shed light on jet variability and the similar physical processes which play a part in it, despite the two AGN being separated by billions of years of cosmic time.

	Promotionskolloquium
Jan Roeder	SCHEDULED

MPIfR

The heart of every galaxy in the universe is home to an awesome monster: a supermassive black hole (SMBH). With masses millions to billions of times that of our sun, they are among the most powerful sources of energy in the Universe. They are surrounded by hot, magnetized plasma, some of which has the unfortunate fate of being accreted and swallowed by the black hole. A small fraction, however, is rescued by magnetic fields – and is ejected thousands of light years into interstellar space, in the form of highly collimated relativistic jets. Such an SMBH-powered system is known as an active galactic nucleus (AGN). Altough AGN have been the subject of active research for almost a century, many aspects of their inner workings remain obscure. In my PhD thesis, I addressed three specific questions, ranging from the very vicinity an SMBH to the far extended jets of AGN: What is the nature of the SMBH at the center of the Milky Way? What is the origin of the observed gamma-ray emission from AGN, and specifically the quasar 3C345? And lastly, how general is our is our established description of AGN as a whole? I have tackled these questions from both an observer's side, using very long baseline interferometry (VLBI) observations of AGN, and from a theorist's side - using general-relativistic hydrodynamics (GRMHD) simulations of exotic black holes and their surroundings. Zoom passcode: 3C345