However, it was not only the galaxies containing jets that showed evidence of mergers!”. “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. “The galaxies that host these relativistic jets give out large amounts of radiation at radio wavelengths,” explains Marco. The team inspected five categories of galaxies for visible signs of recent or ongoing mergers - two types of galaxies with jets, two types of galaxies that had luminous cores but no jets, and a set of regular inactive galaxies. It is these jets that Marco Chiaberge from the Space Telescope Science Institute, USA (also affiliated with Johns Hopkins University, USA and INAF-IRA, Italy) and his team hoped to confirm were the result of galactic mergers. The hot material within the jets is also the origin of radio waves. The two high-speed jets of plasma move almost with the speed of light and stream out in opposite directions at right angles to the disc of matter surrounding the black hole, extending thousands of light-years into space. Whilst most galaxies are thought to host a supermassive black hole, only a small percentage of them are this luminous and fewer still go one step further and form what are known as relativistic jets. The team studied a large selection of galaxies with extremely luminous centres - known as active galactic nuclei (AGNs) - thought to be the result of large quantities of heated matter circling around and being consumed by a supermassive black hole. The results lend significant weight to the case for jets being the result of merging black holes and will be presented in the Astrophysical Journal.Ī team of astronomers using the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 (WFC3) have conducted a large survey to investigate the relationship between galaxies that have undergone mergers and the activity of the supermassive black holes at their cores.

Almost all of the galaxies hosting these jets were found to be merging with another galaxy, or to have done so recently. In the most extensive survey of its kind ever conducted, a team of scientists have found an unambiguous link between the presence of supermassive black holes that power high-speed, radio-signal-emitting jets and the merger history of their host galaxies.

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