Gas clouds are traveling from galaxy to galaxy to feed supermassive black holes. The discovery could help explain how these invisible behemoths evolve in galactic cores until they reach millions of times the mass of the Sun.
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Using data from the New South Wales Telescope in Australia, a team of scientists studied the orbits of stars and gas clouds in more than 3,000 galaxies. In some of them, they found misaligned gases, that is, orbiting the galactic centers in a different direction than the stars in the same galaxy.
These gases are so misaligned (in relation to the other objects in their galaxies), that scientists can conclude that their trajectories were influenced by the interaction between two galaxies. Or rather, these interactions send clouds of gas from one galaxy to another.
Interestingly, most of the galaxies with active supermassive black holes — that is, those that are feeding on matter and emitting radiation from their accretion disks — were those with misaligned gas clouds.
This suggests that there is some link between misaligned gas and the activity of supermassive black holes. According to the authors of the new study, gas is transferred when two galaxies meet and interact gravitationally. When that happens, they have to travel enormous distances in intergalactic space and then onward to the core of their new host galaxy.
At the end of the journey, the misaligned orbiting gas cloud ends up getting too close to the supermassive black hole of its new galactic home. Thus, it is pulled in and swallowed as fuel for the black hole to grow.
The conclusion of the study is that misaligned clouds are evidence of interaction between two galaxies and represent, in most cases, the presence of active black holes in the centers of their host galaxies. With this, the researchers suggest that this mechanism is an important new piece for the evolution of supermassive black holes.
The study was published in the journal Nature Astronomy.
Source: Nature Astronomy; via: phys.org