New Haven, Conn. — Yale astronomer Pieter van Dokkum and a team of researchers have discovered an object in space they call the “Infinity” galaxy — two recently-collided galaxies that, together, look like the symbol for infinity.
And at the center of “Infinity,” embedded in a cloud of gas, they say, is a supermassive black hole.
The findings are described in a new study to be published in The Astrophysical Journal Letters.
The discovery, the researchers say, is intriguing for several reasons. It suggests a novel way for black holes to form, it provides a possible explanation for the existence of incredibly massive black holes in the early universe — and it may be the first direct evidence of a supermassive black hole just after it formed.
“This is as close to a smoking gun as we’re likely ever going to get,” said van Dokkum, the Sol Goldman Family Professor of Astronomy and professor of physics in Yale’s Faculty of Arts and Sciences and lead author of the new study.
Everything about this galaxy, he said, is unusual.
“Not only does it look very strange, but it also has this supermassive black hole that’s accreting a lot of material,” he said. “The biggest surprise of all was that the black hole was not located inside either of the two nuclei of the merging galaxies, but in the middle. We asked ourselves: how can we make sense of this?”
Van Dokkum and astronomer Gabriel Brammer of the University of Copenhagen made the discovery while studying images from the COSMOS-Web survey, which is part of the data archives of NASA’s James Webb Space Telescope.
Van Dokkum also led follow-up observations of the Webb data. In addition, the researchers used W.M. Keck Observatory data for the study, and archival data from the National Radio Astronomy Observatory’s Very Large Array and the Chandra X-ray Observatory.
Finding a black hole that is not located in the nucleus of a massive galaxy is, in itself, unusual, the researchers said. To then discover that the black hole had only just formed was unprecedented.
“In other words, we think we’re witnessing the birth of a supermassive black hole — something that has never been seen before,” van Dokkum said.
The finding also has implications for the ongoing debate about the formation of black holes in the early universe.
One theory — the “light seeds” theory — is that small black holes formed when stars’ cores collapsed and exploded. Eventually, those “light seed” black holes merged into supermassive black holes. This theory, however, would require an extraordinarily long time to reach fruition. And the Webb telescope already has identified supermassive black holes that appeared in the universe too early to be explained by the “light seeds” theory.
That leaves the “heavy seeds” theory, which has been championed by Yale astrophysicist Priyamvada Natarajan and others. This theory suggests that much larger black holes can form from the collapse of large clouds of gas. The sticking point for the “heavy seeds” theory has been that collapsing gas clouds usually form stars.
The Infinity galaxy, however, may show how extreme conditions — including those in the early universe suggested by the “heavy seeds” theory — could lead to the creation of a black hole, van Dokkum said.
“In this case, two disk galaxies collided, forming the ring structures of stars that we see,” he said. “During the collision, the gas within these two galaxies shocks and compresses. This compression might just be enough to have formed a dense knot, that then collapsed into a black hole.
“While such collisions are rare events, similarly extreme gas densities are thought to have been quite common at early cosmic epochs, when galaxies began forming,” he added.
Van Dokkum and his colleagues stressed that additional research is needed to confirm the findings and what they portend for black hole formation.
Co-authors of the study are Natarajan, Josephine F.W. Baggen, Michael Keim, and Imad Pasha, all from Yale, and Brammer, from the University of Copenhagen.