Particle acceleration in the Universe
We explore regions of extended radio emission that are millions of light years in size but cannot be linked to any nearby galaxy. However, this diffuse emission appears to occur only in colliding clusters of galaxies. These collisions are the most energetic events in the present day Universe. The radio filaments are so large they span an area on the sky about half the diameter of the full moon, although they are located at a distance of more than two billion light years. Within the outwards traveling shock waves particles are accelerated to energies more than a million times higher than what can be achieved by the most powerful particle accelerators on Earth. Very little is known about the physics of particle acceleration in these extremely dilute plasmas.
Magnetic fields in the Universe
Magnetic fields are ubiquitous in the cosmos and are taking the center stage in astrophysical research from the smallest scales to the largest systems known in the Universe. They are responsible for stellar activity and govern the relation between planets and their host stars. Magnetic fields are essential for understanding star formation and control the density and distribution of cosmic rays in the Galaxy. On even larger scales, they affect the evolution of galaxies and galaxy clusters. The origin of these magnetic fields in individual astrophysical objects such as our Earth or the Sun as well as in the Universe as a whole is only poorly understood. Theoretical modeling of magnetic fields and their interaction with plasmas is notoriously difficult, and the observational investigation of cosmic magnetic fields remains a challenge even today. With algorithmic advances in adaptive-mesh codes, high-fidelity simulations of magnetic fields have become a reliable instrument for theory on all scales. On the observational side, a new suite of instruments are providing new measurements of and new insights into magnetic fields.
At the University of Hamburg, we have an ideal combination of researchers, from all career stages, to teach the next generation of astrophysicists how to investigate the origin and effects of astrophysical magnetic fields. We work, both, on theory and observations, ranging from stellar to cosmological scales as well as from the very lowest to the highest photon energies. We are involved in the observatories LOFAR, AUGER, CTA, CARMENES, eROSITA, and TIGRE, and have an excellent track record in cosmic-ray propagation studies and magnetohydrodynamical modeling.
Formation of galaxies und clusters of galaxies
How galaxies and clusters of galaxies form is regarded as the most important topic in extragalactic astrophysics and one of the key questions of the EU-Astronet Science Vision document of 2007. Recently, much supporting evidence has been found that the formation of galaxies is intimately linked to the presence of very massive black holes at the centers of big galaxies. Cooling of gas in massive dark matter halos not only leads to star and galaxy formation but also to the growth of black holes. Using LOFAR we expect to make major advances in this field by quantifying the role of radio-loud active galactic nuclei in shaping large-scale structure in the universe. The state of this field was recently summarised in our Nature Review (Cattaneo et al. 2010).