Wednesday, August 4, 2021

Galactic cluster magnetic field can bend black hole jets

Some supermassive black holes at the centers of galaxies are active and eject relativistic jets thousands or even millions of light years away into intergalactic space. And some of them can be very strange, like the jets found in galaxy MRC 0600-399 — they curve bizarrely and split into a T-shape, and a new study suggests that this is caused by gigantic magnetic fields. 

Although galaxies are very distant from each other, even those that are part of the same group, a galactic cluster creates interactions between them that can be observed in X-rays. In other words, they form a hierarchical structure that can only be perceived if observed on a large scale. One such cluster is Abell 3376, of which galaxy MRC 0600-399.

 Like galaxies themselves, clusters have a magnetic field, and the powerful relativistic jets of a black hole may not be immune to the influence of that field. At least that seems to be the case for jets fired by the black hole at the center of MRC 0600-399, according to a new study published in the journal Nature 

 Well, if we consider that the formation of relativistic jets itself may be related to the magnetism of the black hole, and that the jets extend far beyond the extent of their galaxies , it seems reasonable to conclude that an even larger magnetic field from a cluster of galaxies is capable of interfering with the shape of the jets.

The strange formation of relativistic jets in this galaxy was already known, but astronomers have not yet come to a consensus on the cause of something so unusual. With the MeerKAT radio telescope in South Africa, the authors of the new study have achieved observations at much higher resolution than those obtained so far. Upon examining the images, they confirmed that the jets bend at angles of almost 90 degrees, as noted before, but this time there was something unique: diffuse regions on either side of the point where the jet curves, creating a T shape. 

 To better understand what they were looking at, the team ran simulations to try to reproduce the shape of the jet. They found that a black hole jet might be unable to pass through a curved layer of magnetic field, which results in a curvature that follows the shape of the magnetic field itself — more or less like a jet of water when it hits a solid surface, such as glass. 

This is not the only possible explanation, but it is one that best suits all the jet characteristics and the shape of the curvatures. If the hypothesis is correct, it would be a fascinating discovery, because it demonstrates how the presence of colossal magnetic fields in galaxy clusters can influence the environment contained within their domains. Research can also help to better understand the dynamics of galactic clusters.

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