Intergalactic magnetic fields
DOI: 10.1063/1.4796247
Can arise from galactic black holes. Intergalactic voids—the vast regions of the cosmos that are largely empty of galaxies—are permeated by very weak magnetic fields, far less than a microgauss. The “walls” where galaxies and galaxy clusters reside may have fields up to a microgauss. All these fields have most often been thought of as either primordial (arising at the Big Bang) or due to shock waves at massive colliding gas clouds. Now, researchers from the University of Toronto and Los Alamos National Laboratory have found a new source of diffuse cosmic magnetism. They analyzed 100 large radio-loud galaxies: 70 giant ones in isolation and 30 smaller ones in the dense environs of galaxy clusters. They concluded that fully half of the energy content (up to 1060 ergs or more) of the extensive radio-emitting lobes is in magnetic energy thrown out of 108-solar-mass black holes at the cores of the galaxies. Summed over many galaxies, this energy reservoir appears to be the largest available in the mature universe for magnetizing intergalactic space. Furthermore, because the lobes have a higher pressure than the surrounding intergalactic medium, even when the central black hole has “turned off,” the lobes with their force-free fields will expand into the IGM. These expelled magnetic fields should exert a substantial influence on subsequent galaxy and large-structure formation. (
