Powerful Jets From a Black Hole are Spawning Star Clusters

Supermassive black holes are messy feeders, and when they’re gorging on too much material, they can hurl high-energy jets into the surrounding Universe. Astronomers have found one of the most powerful eruptions ever seen, emanating from a black hole 3.8 billion light-years away. The powerful jets are blowing out cavities in intergalactic space and triggering the formation of a huge chain of star clusters.

The black hole is part of a massive galaxy cluster, named SDSS J1531, which contains hundreds of individual galaxies, and all these galaxies have huge reservoirs of hot gas and dark matter. Using several telescopes for multiwavelength observations — including the Chandra X-ray Observatory, the Low Frequency Array (LOFAR) radio telescope, the Atacama Large Millimeter and submillimeter Array (ALMA), the Gemini North telescope’s Gemini Multi-Object Spectrograph (GMOS), and the Very Large Array (VLA) — astronomers were able to discern that two of the central galaxies were engaged in a major merger. The merger activated the supermassive black hole in the center of one of the large galaxies, which produced an extremely powerful jet. As the jet moved through space, it pushed the surrounding hot gas away from the black hole, creating a gigantic cavity.

The merger and the resulting jets from the black hole created a remarkable and stunning chain of 19 young stellar superclusters wound the two galaxies like a string of beads.

In their paper, the astronomers said the dynamic environment of SDSS J1531 offers an excellent laboratory to study the interplay between mergers, and their multiwavelength studies allowed them to uncover the origin and evolution of the “beads on a string” star formation complex.

“We’ve reconstructed a likely sequence of events in this cluster that occurred over a vast range of distances and times,” said co-author Grant Tremblay, from the Harvard & Smithsonian Center for Astrophysics CfA). “It began with the black hole a tiny fraction of a light-year across forming a cavity almost 500,000 light-years wide. This single event set in motion the formation of the young star clusters nearly 200 million years later, each a few thousand light-years across.”

Chandra’s X-ray vision allowed the scientists to see wing-shaped emissions in bright X-rays, which traced dense gas near the center of SDSS J1531. The said these wings make up the edge of the cavity, and then LOFAR revealed radio waves from the remains of the jet’s energetic particles filling in the giant cavity. Together, these data provide compelling evidence of an ancient, massive explosion.

Osase Omoruyi, also from CfA who led the study, compared finding this cavity to unearthing a buried fossil.

“We are already looking at this system as it existed four billion years ago, not long after the Earth formed,” she said. “This ancient cavity, a fossil of the black hole’s effect on the host galaxy and its surroundings, tells us about a key event that happened nearly 200 million years earlier in the cluster’s history.”

You can learn more about a Hubble Space Telescope view of this supercluster back in 2014.

The astronomers said that some of the hot gas pushed away from the black hole eventually cooled to form cold and warm gas. The team thinks tidal effects from the two merging galaxies compressed the gas along curved paths, leading to the star clusters forming in the bead-like pattern.

Omoruyi and her colleagues could only see radio waves and a cavity from one jet, but black holes usually fire two jets in opposite directions. This led them to surmise that the radio and X-ray signals from the jet in the other direction might have faded to the point that they are undetectable.

“We think our evidence for this huge eruption is strong, but more observations with Chandra and LOFAR would clinch the case,” said Omoruyi. “We hope to learn more about the origin of the cavity we’ve already detected, and find the one expected on the other side of the black hole.”