Shedding light on galactic evolution

A multi-national team of researchers has determined that previously measured large-scale magnetic fields are unambiguously associated with normal galaxies.

The galaxies lie in front of background quasars, whose light is affected by the magnetic fields in the galaxies, but also potentially by the magnetic field of the galaxy that hosts the quasar.

Using data collected with the European Southern Observatory’s 8-m Very Large Telescope, the team, led by Francesco Miniati from ETH Zürich, Switzerland, demonstrated that the quasar host galaxies are not where the fields are located. When the Universe was only one-third of its present age, the magnetic fields in and around normal galaxies were already of comparable strength to those observed today, according to the team.

This indicates that magnetic fields build up inside galaxies at an unexpectedly fast rate. So-called ‘dynamo mechanisms’, operating partly via interstellar turbulence, are thought to be responsible for this growth.

The team’s research, published in Nature this week, offers a glimpse into the origin and growth of magnetic fields in today’s galaxies. Very little is known about how they develop over cosmic time, because of the difficulty of detecting magnetic fields in the distant Universe.

The team notes that their findings serve as a general reminder of the potential importance of magnetic fields in the formation and evolution of cosmic structures in our Universe.