Chandra Joins In Discovery of Infinity Galaxy and Possible Newborn Black Hole

The Infinity Galaxy
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Credit: X-ray: NASA/CXC/Yale Univ./P. van Dokkum et al.; Infrared: NASA/ESA/CSA/STScI/JWST; Image Processing:NASA/CXC/SAO/N. Wolk; NASA/ESA/CSA/STScI/A. Pagan

Scientists have discovered an oddly-shaped galaxy that may contain the first newborn supermassive black hole ever spotted. If confirmed, this result implies that black holes can form remarkably quickly, not just soon after the Big Bang but throughout cosmic time.

Astronomers found a galaxy they call the Infinity Galaxy by sifting through data in NASA’s James Webb Space Telescope archive. (They gave it this nickname because it resembles the horizontal hourglass-like symbol for infinity.) Consisting of two rings of stars and gas seen in the Webb data, the Infinity Galaxy likely formed from the collision of two galaxies. The galaxy is about eight billion light-years from Earth. 

The unusual appearance of the Infinity Galaxy prompted the team to examine it using archival X-ray data from NASA’s Chandra X-ray Observatory and radio data from the NSF’s Karl G. Jansky Very Large Array (VLA). Together, these telescopes uncovered a growing supermassive black hole in this galaxy. 

The discovery of the huge black hole is important because it may give astronomers direct evidence of a supermassive black hole detected soon after it formed, which would be a first. It also supports a particular theory that explains how supermassive black holes can rapidly form and grow. In this scenario, supermassive black holes are created quickly when giant clouds of gas and dust collapse onto themselves. The theory was developed to explain the existence of massive black holes that formed only a few hundred million years after the Big Bang. 

The location of the supermassive black hole provided a vital hint about its unusual nature. These black holes are usually found in the centers of massive galaxies, but the Chandra and VLA data may show that this is not the case for the Infinity Galaxy. The VLA data suggests the supermassive black hole is not located in the nucleus of either galaxy, but is in between both galaxies in a cloud of gas. The Chandra data unambiguously reveals the presence of a growing black hole near the center of the galaxy.

“Everything is unusual about this galaxy,” said Pieter van Dokkum of Yale University, who led the study. “Not only does it look very strange, but it also has this supermassive black hole that’s accreting a lot of material. 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?”

The black hole in the Infinity Galaxy could have formed in the cloud of gas, or it could have traveled there from another location. Another possibility is that it could be in the center of a third galaxy that is much fainter. If the black hole traveled there from another location or is in another galaxy it would likely have a velocity of motion with respect to us that is different from the gas cloud’s velocity in the Infinity Galaxy. 

Therefore, to decide between the possible explanations for the black hole’s location, the team proposed for new Webb data to compare the velocity of the black hole with the velocity of the gas. Based on preliminary analysis of the new data, they found out that the velocities are strikingly similar.

The team concluded that the supermassive black hole formed within the cloud of gas and that it did so recently, on cosmic timescales, after the collision of the galaxies about 50 million years earlier. The finding has significant implications for recent debates about how black holes can reach immense masses so quickly after the Big Bang.

One theory — the “light seeds” theory — is that supermassive black holes began their lives as small black holes that formed when massive stars collapsed. Eventually, those “light seed” black holes, weighing between about ten and a hundred times the mass of the Sun, would grow into supermassive black holes. This formation path, however, would likely require too much time to assemble the supermassive black holes observed by Webb soon after the Big Bang.

That leaves the “heavy seeds” theory, which has been proposed by the Yale astrophysicist, Priyamvada Natarajan, a co-author on this study, and others. This theory suggests that much larger black holes, weighing between about ten thousand and a hundred thousand Suns, can form from the direct collapse of large clouds of gas. 

“We reported on the first evidence for the formation of such direct collapse heavy seeds using the combined power of Webb and Chandra to detect the galaxy UHZ1, in place when the universe was merely 470 million years old,” said Natarajan. 

A major problem with forming a black hole out of a gas cloud is that these clouds tend to form stars instead as they collapse. Special conditions are required to prevent the formation of stars, involving gas with high densities and unusually low amounts of elements heavier than helium. Natarajan and collaborators have shown that these conditions likely existed in the very early Universe, but it was unclear whether they occur more recently.

“This black hole would have formed over five billion years after the Big Bang, much later than UHZ1,” said Natarajan. “So, what is exciting about the discovery of the Infinity galaxy is that it hints that nature likely makes black holes via direct collapse throughout cosmic time.”

The discovery of this black hole implies that the extreme conditions necessary to form black holes soon after the big bang may also exist much more recently.

“In this case, two disk galaxies collided, forming the ring structures of stars that we see,” van Dokkum said. “During the collision, the gas within these two galaxies shocks and compresses. This compression might just be enough to form a dense knot that then collapsed into a black hole.”

Van Dokkum and his colleagues stressed that additional research is needed to confirm the findings and what they portend for black hole formation.

A paper that discusses the Webb, Chandra and VLA observations of the Infinity Galaxy has been accepted for publication in the Astrophysical Journal Letters and a preprint is here. The full author list is Pieter van Dokkum from Yale, Gabriel Brammer from the University of Copenhagen, and Josephine F.W. Baggen, Michael Keim, Priyamvada Natarajan and Imad Pasha, all from Yale. A separate paper led by van Dokkum with the newer Webb data is currently being reviewed at the Astrophysical Journal Letters and the submitted version is available online.