Dwarf galaxies and the Magnetisation of the IGM
  With the operation of LOFAR, a great opportunity exists to shed light on a
problemof some cosmological significance. Diffuse radio synchrotron emission
not associated to any obvious discrete sources as well as Faraday rotation in
clusters of galaxies both indicate that the intergalactic or intracluster
medium (IGM, ICM) is pervaded by a weak magnetic field, along with a population
of relativistic particles. Both, particles and fields must have been injected
into the IGM either by Active Galactic Nuclei (AGN) or by normal starforming
galaxies. Excellent candidates for the latter are starburst dwarf galaxies,
which in the framework of hierarchical structure formation must have been
around in large numbers. If this is true, one should be able to detect extended
synchrotron halos of formerly highly relativistic particles around local
starburst or post-starburst dwarf galaxies. With LOFAR, one should easily find
these out to the Coma Cluster and beyond.
