personal website

 
 

Research
   
 
I am doing research in observational cosmology and high energy astrophysics. My research interests are mainly in understanding how and where Active Galactic Nuclei (AGNs) form in the Universe.
 
What are AGNs?
Every galaxy almost certainly contains a super-massive black hole (SMBH; several million to billion solar masses) in its center. Some processes cause matter to end up in the immediate vicinity of the SMBH. Because of conservation of angular momentum this material falls not directly onto a SMBH, but creates a so-called accretion disk around the SMBH before it is finally devoured by the SMBH. The accretion of matter onto a SMBH is one of the most efficient ways of producing electromagnetic radiation in the Universe. This center region of the galaxy outshines the entire rest of galaxy (that is the reason why these objects are called AGNs – active galactic nuclei) for several million years before the SMBH has accreted all the matter, the central engine shuts down, and the object can be observed as a normal galaxy again.

I am fascinated by these objects because the radiation originates from matter under extreme conditions. Furthermore, AGNs are among the most energetic phenomena in the Universe.
 
What am I researching currently?
 
Since AGNs are so bright, they can be seen across almost the whole Universe and can be used as tracers of matter in the Universe across cosmological time. In one of my current projects, I measure the distribution of AGNs in the Universe. This allows constraints on why and what kind of normal galaxies turn into an AGN and how AGNs co-evolve with their host galaxies. Furthermore, I am studying a particular class of AGNs, the so-called Compton-thick AGNs, that are surrounded by so much gas and dust that it is extremely difficult to detect them at all. However, this class of AGNs could make up a large fraction of all AGNs in the Universe and is needed to explain the observed spectrum of the cosmic X-ray background.