My main research field are galaxy clusters. In particular, I am working on methods to detect clusters using weak gravitational lensing. These have the advantage that such a sample is unbiased by the luminosities and the dynamical states of the clusters. This involves working with large and very large data sets of wide field imaging data (currently the Garching-Bonn Deep Survey and Pan-STARRS).
In two smaller projects I am investigating the interaction of merging double clusters, in particular their dark matter and X-ray properties, and a supercluster of galaxies at z=0.4 which we detected recently using weak lensing methods.
Recently I got hooked by fossil groups and fossil clusters, of which it is not yet clear if they form a separate class of objects by themselves, or just represent the latest stages of mass assembly in the Universe.
All this data wants to be reduced, as it does not pop out of our telescopes in a ready-to-use form. As our requirements concerning data quality are very high, we have to develop the software ourselves. This is the basis for my second main occupation:
We developed THELI, a fully automatic pipeline for imaging data reduction. It runs on data of any kind of imaging instrument, let it be single- or multi-chip cameras for the optical, near-IR or mid-IR. My current focus is on the developent of graphical user interfaces and techniques for the optimum reduction of infrared data. THELI is free software and can be downloaded from ftp://ftp.ing.iac.es/mischa/THELI/
Still very much in its infancy is a similar tool for the reduction of longslit and multi-object spectroscopic data, again for optical and infrared wavelengths.
With colleagues in Sweden we are investigating the properties of Supernova remnants. In particular the Crab nebula is here of interest as it still did not give away its largest secret: That of the missing several solar masses that should be there, but have not been found despite intensive searches over the last three decades.
Interacting galaxies, tidal tails and dwarf galaxies
This includes several different studies. A census of tidal tails in distant galaxies, as well as the search for yet unknown tidal tails in near-by systems that, given their appearance, should have tidal tails which so far evaded their detection.
Related to this is the search for extremely low surface brightness galaxies. According to the standard cold dark matter model, these should exist in large numbers. However, they are exceedingly difficult to detect, posing a problem for both observations and theory.
Ancient planetary nebulae
I got interested in those only recently, so I would not label this as an active research area. So far, I am more fascinated by the challenge of detecting these elusive structures at all. For example, Jacoby 1 has been discovered only in 1995 around an extremely hot white dwarf and was imaged only once more in 1996. A 10 hour exposure in [OIII] which I made in 2007 revealed an yet unknown shock front, evidence of interaction with the ISM. This requires follow-up observations with larger telescopes.