The group is funded for five years by the DFG (German Science Foundation) in the Emmy Noether Programme.
The project consists of three parts: (a) development, test and employment of new methods to utilise these instruments in searches for gravitational lenses, especially with extended sources; (b) improve the established and develop new methods to analyse radio observations of lens systems in order to maximise the information gain for a wide field of astrophysical research; (c) apply the novel methods for a systematic and quantitative interpretation of source and lens properties, especially global and central mass profiles, ellipticities and substructure. With these results we will answer the most important questions concerning the structure and evolution of galaxies.
The aim of this project is to take advantage of the opportunities the new generation of radio telescopes offer for gravitational lens research. We concentrate on radio lenses for several reasons. Radio telescopes provide the widest range of resolutions available at any band and allow the study of structures down to sub-mas scales. In addition, effects of dust extinction and microlensing, which complicate the optical study of lenses (see our investigation of both in Wucknitz et al., 2003), are usually negligible at radio wavelengths.
We will develop, test and finally apply the optimal strategies to fully explore the capabilities of these revolutionary new instruments for an ambitious science project in the field of gravitational lenses. In this way our field will be a major science driver at the forefront of cutting-edge technology progress. Our work will also serve as pathfinder for later use of the "Square Kilometer Array" (SKA) for lensing studies, just as LOFAR is a pathfinder for the SKA. The project consists of three main parts:
Our project with its special need for high resolution will be a major science driver for the extension of LOFAR into Germany. By establishing a group that will work with LOFAR data from the very beginning and with a detailed project plan, we will assure an early success of German LOFAR. The proposed project is the only one with specific plans to use LOFAR for lens searches, which gives us an outstanding lead compared to other groups working on lens surveys. We will exploit this advantage and conduct a lens search finding the largest number of systems so far.
New radio interferometric mapping methods will first be implemented for the unlensed case. In this way our work uses gravitational lensing as science driver for the development of novel imaging techniques in radio interferometry. Currently the classical Clean method (Högbom, 1974) is still the workhorse of most work in radio mapping, even though its shortcomings are well known. Inspiration from our field will form an important trigger to bring the development in this sector to new life.
In the implementation for the lensed case, the new methods will allow us to determine more accurate lens mass models and to reconstruct the true source structures (utilising the lens as natural telescope) with new levels of accuracy. The applicant's version of LensClean is currently by far the most sophisticated method for the modelling of radio lenses. By continuing the development and by introducing new concepts we will assure to remain world-leading in this field.
Most important goal is the systematic determination of the mass distributions of a large number of medium and high redshift galaxies. This homogeneous sample will provide the information needed to solve the most important questions concerning the structure and evolution of galaxies. Additionally the magnifying lens effect will be used to study the background sources in greater detail.
Combining the work on surveys, the analysis methods and the application of the methods to detailed observations in one research group is the optimal way to achieve the best results in all three fields, especially because the methods overlap. In this way each subproject can provide input for the other projects immediately and directly. Seeing how the efforts in all three fields are necessary to produce valuable results also guarantees to keep the motivation of all co-workers at the highest level. Students working in the project will have the opportunity to contribute to a wide field of tasks and get in contact with the world-leading groups in the field.