Joint Astrophysics Colloquium

The Origin of Magnetic Fields in Galaxies:
What Should to See at High Redshifts?

Ethan Vishniac

McMaster University

Spiral galaxies, including our own, have magnetic fields embedded in the gas of their disks. These fields are typically coherent and have an energy density comparable to the turbulent energy density of the interstellar medium. Conventional dynamo theory has some difficulty explaining the existence of these fields at the current epoch, so recent observations showing that magnetic fields with comparable amplitudes were present when the universe was about a billion years old have come as a surprise. I will review the arguments for weak seed fields from the early universe, and show that turbulent processes in young galaxies can explain these results. I argue that observations of magnetic fields at high redshift cannot be used to argue for novel processes in the early universe.