Welcome to my homepage dedicated to my professional life as an observing astrophysicist. I work on the centers of nearby galaxies, trying to observe and understand the immediate surroundings of the supermassive black holes (SMBH) that lurk there. Many of these SMBH actively accrete material from their surroundings creating "bright fireworks" that can be observed all throughout the electromagnetic spectrum.
Here you will not only find all relevant information about me and my research but I will also post once in a while interesting information I encounter during my work.
Please feel free to contact me in case of questions or comments!
some WISE related routines, e.g., for converting the magnitudes into flux densities
Most of the routines are documented and should be self-explanatory but I am still working on a more detailed documentation, version control/history and so on. Please let me know if you have any questions!
During my time as ESO fellow, working at the Paranal Observatory, I was lucky enough to record this mid-infrared image with VISIR during one of those winter nights in 2016 as part of my service to the community:
Slides of my practical lecture on how to write observing proposals (for big telescopes like the VLT of ESO), held as part of the International School of Astrophysics on The current and future observing facilities: A guided Tour, Belgrade, Serbia
Colloquium talk given at the University of Belgrade in 2017 as an overview of ESO and how to apply for observing time
The European Southern Observatory (ESO) is the leading astronomical observatory in the world operating three world-class sites all situated in the Atacama desert in Chile. It offers access to all its telescopes to all astronomers world-wide not only to its members. This includes state-of-the-art observations as a community service but all excellent opportunities to work directly at ESO at all career stages. I will give a quick overview of ESO's observing facilities and show how to access them including advice on proposal writing. In the final part, the ESO fellow and studentship programmes in hosted Germany and Chile will be presented. This presentation is planned to be very informal and interactive so that we can concentrate on the main interests of the audience.
Colloquium talk given at the Observatory of Belgrade in 2017 as an overview of high angular resolution imaging of AGN The nuclei of many galaxies shine bright throughout all the electromagnetic spectrum. This powerful emission if often brighter than all the star light of the galaxy combined. Its source is an accreting supermassive black hole in the galaxy center. However, around half of the accretion disk emission does not escape the nuclear region but is instead absorbed by an unknown dust structure and reemitted in the infrared. I will present an overview of our attempts to detect and resolve this dust structure in nearby active galactic nuclei (AGN) and review the surprising results emerging from recent highest angular resolution observations.
We present the first subarcsecond-resolution mid-infrared (MIR) atlas of local active galactic nuclei (AGN) containing 253 objects with a median redshift of z = 0.016. It comprises all available MIR imaging observations performed to date with ground-based 8-meter class telescopes and includes in total 895 independent photometric measurements, of which more than 60% are previously unpublished.We detect extended nuclear emission in at least 21% of the objects, while another 19% appear clearly point-like, and the remaining objects cannot be constrained. Subarcsecond resolution allows us to isolate the emission of the AGN on scales of a few tens of parsecs for the bulk of the sample and obtain nuclear photometry in multiple filters for the objects. The photometry is used to construct median spectral energy distributions (SEDs) for the different optical AGN types and estimate the individual MIR 12 and 18 um continuum luminosities, which range over more than six orders of magnitude. We also analyse the arcsecond-scale MIR emission as probed by Spitzer and compare it to the subarcsecond-scale emission. The continuum emission is on average 20% lower on subarcsecond scales with a large scatter that depends mostly on the object distance or luminosity. The silicate feature strength is similar on both scales and generally appears in emission (absorption) in type I (II) AGN. However, the PAH emission appears weaker or absent on subarcsecond scales, indicating that most of the star formation has been resolved out. The differences of the MIR SEDs on both scales are particularly large for AGN/starburst composites and close-by (and weak) AGN. Because of its size and characteristics, the AGN MIR atlas is well-suited not only for detailed investigation of individual sources but also for sample studies of AGN unification.
This is the submission version of the mid-infrared atlas paper (451 pages, 930 Figures, ~50MB, submitted to MNRAS).