Radio Jet Sprays Can Reveal Two Black Holes Canoodling

The Hubble Space Telescope has helped scientists identify a telltale marker of galactic merger.

Astronomers surveyed several galaxies, categorizing them based on luminosity. Some super-massive galaxies had luminous cores which also shot out jets associated with radio emissions. Only a small percentage of galaxies are luminous and an even smaller percentage has observable jets of plasma shooting out from centers. The luminosity in the cores is attributed to heated matter circling super-massive black holes.

The survey team found nearly all galaxies shooting jets had experienced merger.

"By using Hubble's WFC3 camera we found that almost all of the galaxies with large amounts of radio emission, implying the presence of jets, were associated with mergers. However, it was not only the galaxies containing jets that showed evidence of mergers!" said Marco Chiaberge, one of the study authors.

To explain why some mergers to produce super-massive black holes were associated with jets, researchers theorize relative size of merging black holes could be the key.

"A merger between two massive galaxies causes two black holes of a similar mass to also merge. It could be that a particular breed of merger between two black holes produces a single spinning supermassive black hole, accounting for the production of jets," said co-author Colin Norman.