Magnetic fields present in the early universe may have shrunk the volume of our galaxy by nearly 30 per cent. These fields seem to concentrate matter in the centre of galaxies, which might help explain why some black holes in such locations grow so fast.
Sergio Martin-Alvarez at the University of Cambridge and his colleagues simulated the effects of poorly understood primordial magnetic fields on galaxy formation.
Computer simulations of galaxy formation don鈥檛 usually take these fields into account, Martin-Alvarez says.
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鈥淚t鈥檚 a very important parameter that is often overlooked because it is so hard to understand theoretically,鈥� he says. 鈥淏ut it could change potentially everything we know about the early stages of the universe to even modern day.鈥�
Looking at a simulated galaxy with a similar size, shape and conditions to those of the Milky Way, the researchers found that by removing these magnetic fields altogether, the galaxy鈥檚 volume grew to about 45 per cent larger than it would have otherwise been.
The researchers suggest that the magnetic fields shrunk galaxies in the early universe by keeping gases closer together at the onset of galaxy formation, compressing galaxies towards their centres.
This may also help explain why supermassive black holes are often found at the centre of galaxies and why they grow so fast, says Martin-Alvarez. 鈥淚f a galaxy is concentrated at its centre, you have more material to feed into a black hole, and so you can grow its mass very quickly,鈥� he says.
鈥淢agnetic fields are鈥β爋ne of the most important unexplored phenomena in many astrophysical situations,鈥� says Andrew Jaffe at Imperial College London. 鈥淸This work] gives some tentative picture of when the effects of magnetic fields might become important.鈥�
Reference: arXiv, DOI:
