Dwarf galaxies and the Magnetisation of the IGM

TL;DR

This paper discusses how LOFAR observations can detect synchrotron halos around dwarf galaxies, shedding light on the magnetisation of the intergalactic medium by relativistic particles injected from star-forming galaxies.

Contribution

It proposes that starburst dwarf galaxies significantly contribute to IGM magnetisation and predicts LOFAR can detect their extended synchrotron halos.

Findings

LOFAR can detect synchrotron halos around dwarf galaxies.

Starburst dwarf galaxies are key sources of IGM magnetic fields.

Extended halos can be observed out to the Coma Cluster.

Abstract

With the operation of LOFAR, a great opportunity exists to shed light on a problemof some cosmological significance. Diffuse radio synchrotron emission not associated to any obvious discrete sources as well as Faraday rotation in clusters of galaxies both indicate that the intergalactic or intracluster medium (IGM, ICM) is pervaded by a weak magnetic field, along with a population of relativistic particles. Both, particles and fields must have been injected into the IGM either by Active Galactic Nuclei (AGN) or by normal starforming galaxies. Excellent candidates for the latter are starburst dwarf galaxies, which in the framework of hierarchical structure formation must have been around in large numbers. If this is true, one should be able to detect extended synchrotron halos of formerly highly relativistic particles around local starburst or post-starburst dwarf galaxies. With LOFAR, one should easily find these out to the Coma Cluster and beyond.