Nordita Astrophysics Seminars

Signatures of magnetic fields in the young galaxies

by Jennifer Schober (Nordita)

Local galaxies are in a state of "energy equipartition", meaning kinetic, thermal, and magnetic energy density being comparable. Recent studies of galaxy formation suggest that the small-scale dynamo can produce strong magnetic fields by randomly stretching, twisting, and folding the field lines already in primordial minihalos. Due to the large growth rate of the dynamo, the equipartition field strength is reached within only a few Myrs. A signature of magnetic fields is synchrotron emission from cosmic ray electrons spiralling around the field lines. With the strength of magnetic fields being high from early on, we expect significant non-thermal radio emission also from distant galaxies. We use a semi-anlytical galaxy model to determine the synchrotron flux as a function of redshift while assuming energy equipartition. We find that synchrotron emission can be detected up to cosmological redshifts with current and future radio telescopes. This provides an observational test for the evolution of galactic magnetic fields.