Observing the history of galactic magnetic fields

While most of my research is purely theoretical, I recently also became interested in finding observational signatures of magnetic fields. The latter are crucial to verify (or falsify?) our current picture of the magnetic history of galaxies.

Nature provides us with a very important tool to study magnetic fields indirectly – cosmic rays. These are charged particles, e.g. electrons, protons, and heavier atomic nuclei, that move at relativistic velocities. Their origin is believed to lie in the shocks from exploding stars, so-called supernovae. As cosmic rays carry a charge they interact with the magnetic field of a galaxy. They get deflected and move in spirals around the field lines which leads to the emission of synchrotron radiation. The intensity of this radiation depends on the strength of the magnetic field.

One of my current projects involves modelling the population of cosmic rays in a galaxy. Therefore, I take into account the general properties of a galaxy, like for example its star formation rate, and their evolution throughout the galactic lifetime. I estimate the resulting synchrotron radiation for our model of the turbulent magnetic field amplification. With the future generation of radio telescopes, including for example the SKA (Square Kilometer Array), the prediction from my models can be tested.


Figure:  The VLA (“Very Large Array”) in New Mexico can be used to observe synchrotron emission, a signature of magnetic fields, from very distant galaxies.

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