This image of the ‘jellyfish’ galaxy JO204 shows clearly how material is streaming out of the galaxy in long tendrils to the lower-left; red shows the glow from ionized hydrogen gas and the whiter regions are where most of the stars in the galaxy are located; some more distant galaxies are also visible. Image credit: ESO / GASP Collaboration.
MUSE Observations of ‘Jellyfish’ Galaxies Reveal New Way to Fuel Supermassive Black Hole
‘Jellyfish’ galaxies can be found only in galaxy clusters and are very rare: to date, just over 400 candidate galaxies have been found.
The ‘tentacles’ of these galaxies are produced in galaxy clusters by a process called ram-pressure stripping. Their mutual gravitational attraction causes galaxies to fall at high speed into galaxy clusters, where they encounter a hot, dense gas which acts like a powerful wind, forcing tails of gas out of the galaxy’s disc and triggering starbursts within it.
Six out of the seven jellyfish galaxies observed by Dr. Poggianti and co-authors were found to host a supermassive black hole at the center, feeding on the surrounding gas. This fraction is unexpectedly high — among galaxies in general the fraction 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,” Dr. Poggianti said.
“It seems that the central black hole is being fed because some of the gas, rather than being removed, reaches the galaxy center.”