Wednesday, October 14, 2009 - 3:15pm
Rainer Beck (MPIfR Bonn):
"Structure and evolution of magnetic fields in galaxies"
Abstract. Results from simulations of hierarchical structure formation cosmology provide a tool to develop an evolutionary model of regular magnetic fields coupled to galaxy formation and evolution. The dynamo theory allowed us to derive the timescales of amplification and ordering of magnetic fields in disk galaxies. -- The strength and structure of interstellar magnetic fields has been studied by observations of radio continuum emission, its polarization and its Faraday rotation. Fields with a well-ordered spiral structure exist in grand-design, barred, flocculent and even in irregular galaxies. Total field strengths in spiral arms and bars 10 - 30 MicroGauss. In spiral galaxies the fields are aligned parallel to the optical spiral arms, but the strongest regular fields are found in interarm regions. Faraday rotation of polarization vectors in a few spiral galaxies have large-scale structures, probably signatures of coherent fields generated by dynamos. Magnetic fields in galactic halos reveal X-shaped polarization patterns which require gas outflows and dynamo action.