(CN) – New research has uncovered active supermassive black holes in six out of seven “jellyfish” galaxies reviewed, a surprising trend that reveals a previously unknown mechanism by which these cosmic enigmas are fed.
Published Wednesday in the journal Nature, the study focuses on extreme examples of jellyfish galaxies, which are named after the extensive “tentacles” of material that reach tens of thousands of light-years beyond their galactic discs.
The tentacles of these galaxies are produced in galaxy clusters through a process called ram pressure stripping. Their mutual gravitational attraction prompts galaxies to fall rapidly into galaxy clusters, where they encounter dense, hot gas that serves as a powerful wind that ejects tails of gas from the galaxy’s disc and triggers starbursts within it.
Astronomers discovered active supermassive black holes – feeding on surrounding gas – in six of the seven jellyfish galaxies reviewed for the study, an unexpectedly high percentage as the fraction for galaxies in general is less than one in ten.
“This strong link between ram pressure stripping and active black holes was not predicted and has never been reported before,” said team leader Bianca Poggianti, an astronomer at the INAF-Astronomical Observatory of Padova in Italy. “It seems that the central black hole is being fed because some of the gas, rather than being removed, reaches the galaxy center.”
While supermassive black holes are present in nearly all galaxies, only a small fraction discovered so far are active. This led astronomers to wonder why only a few accrete matter and shine brightly. The findings present a newly discovered process by which these black holes can be fed.
“These MUSE (Multi-Unit Spectroscopic Explorer) observations suggest a novel mechanism for gas to be funneled toward the black hole’s neighborhood,” said Yara Jaffe, a European Space Observatory fellow and study contributor. “This result is important because it provides a new piece in the puzzle of the poorly understood connections between supermassive black holes and their host galaxies.”
The new observations are part of a larger, ongoing study of many more jellyfish galaxies.
“This survey, when completed, will reveal how many, and which, gas-rich galaxies entering clusters go through a period of increased activity at their cores,” Poggianti said. “A long-standing puzzle in astronomy has been to understand how galaxies form and change in our expanding and evolving universe.
“Jellyfish galaxies are a key to understanding galaxy evolution as they are galaxies caught in the middle of a dramatic transformation.”
The team observed the galaxies using the MUSE instrument on the Very Large Telescope (VLT) at the European Space Observatory’s Paranal Observatory in Chile.