Strong magnetic fields in normal galaxies at high redshifts

Understand

The origin and growth of magnetic fields in galaxies is still something of an enigma.

• It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale.
• It has recently been demonstrated that field strengths as traced by rotation measures of distant quasars are comparable to those seen today, but it was unclear whether the high fields were in the exotic environments of the quasars themselves or distributed along the line of sight.
• Here we demonstrate that the quasars with strong MgII absorption lines are unambiguously associated with larger rotation measures.