Strong magnetic fields in normal galaxies at high redshifts

TL;DR

This paper provides evidence that normal galaxies at high redshifts possess strong, organized magnetic fields, challenging previous assumptions about the timescale of magnetic field amplification in galaxies.

Contribution

It demonstrates a clear association between strong magnetic fields and normal galaxy haloes at high redshifts using quasar rotation measures and MgII absorption lines.

Findings

Strong magnetic fields are present in normal galaxies at high redshifts.

Magnetic fields are associated with galaxy haloes, not just quasars.

High magnetic field strengths are observed when the universe was about one-third of its current age.

Abstract

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. Since MgII absorption occurs in the haloes of normal galaxies along the sightline to the quasars, this association requires that organized fields of surprisingly high strength are associated with normal galaxies when the Universe was only about one-third of its present age.