Discovery of Infinity galaxy provides evidence of a new pathway for black hole formation
Media Contact: Meagan O’Shea
Maunakea, Hawaiʻi – Astronomers using the W. M. Keck Observatory on Maunakea, Hawaiʻi Island have discovered a cosmic oddity they’ve nicknamed the “Infinity” galaxy — the result of two galaxies colliding to form a shape resembling the infinity symbol. At its center, wrapped in a cloud of gas, may lie something that has never been seen before: a newly formed supermassive black hole.
The discovery is remarkable not just for its shape, but for what it could reveal: a new pathway for black hole formation, a clue to how some black holes in the early universe grew so massive so quickly — and what may be the first direct glimpse of a supermassive black hole in the moments after it formed.
“We think we’re witnessing the birth of a supermassive black hole — something that has never been seen before,” said Pieter van Dokkum, professor of astronomy and physics at Yale University and lead author of the new study. “This is as close to a smoking gun as we’re likely ever going to get.”
The study, led by Yale University, is published in today’s issue of The Astrophysical Journal Letters.
“Everything is unusual about this galaxy,” he said. “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?”
Van Dokkum and astronomer Gabriel Brammer of the University of Copenhagen made the initial discovery while studying images from the COSMOS-Web survey, which is part of the data archives of NASA’s James Webb Space Telescope.
Follow-up observations of the Webb data were conducted using data from the National Radio Astronomy Observatory’s Very Large Array, the Chandra X-ray Observatory, and Keck Observatory, which allowed the team to make several key observations critical for the object’s interpretation.
Using Keck’s Low-Resolution Imaging Spectrometer (LRIS), van Dokkum and the team were able to obtain the spectra that provided essential measurements, including the distance to the Infinity galaxy, the location of the newly formed black hole, and the mass of the black hole: about a million times the mass of the sun, and similar to the mass of the black hole at the center of our Milky Way. “This is a prime example of the crucial role Keck Observatory plays in following up on unusual objects spotted in JWST images,” said van Dokkum. “Thanks to the flexibility of Keck’s observing model—where astronomers can decide in real time what to observe—we’re able to act quickly and pursue high-risk, high-reward targets that other observatories, with fixed programs, simply can’t. The Keck/Yale partnership has been absolutely critical for this and many other discoveries, and this discovery pipeline will only grow stronger with the advent of Roman and the next generation of powerful Keck instruments.”
Black Hole Formation: A Tale of Two Seed Theories
Finding a black hole that is not located in the nucleus of a massive galaxy is, in itself, unusual. To then discover that the black hole had only just formed is unprecedented.
The finding also has implications for recent debates 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. Building a supermassive black hole takes a long time in this theory; however, the Webb telescope already has identified supermassive black holes at a point in the universe that may be too early for the “light seeds” theory to explain.
That leaves the “heavy seeds” theory, which suggests that large black holes can form “in one go” 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.
Van Dokkum said the Infinity galaxy 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.
“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 shocked and compressed. This compression might just be enough to form 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.
“One thing we’d like to do is get closer to the black hole, to see what the gas is doing in its immediate vicinity,” van Dokkum said. “Later this fall, we will use Keck Observatory’s adaptive optics to conduct this research.”
“Apart from that,” adds van Dokkum, “the ball is in the theorists’ court! We need computer models that simulate the extreme conditions during the collision, to see if – in the simulations – a black hole forms. In a galaxy unimaginably far from Earth, the universe just made a black hole. And in doing so, it handed us a clue about how our own Milky Way was born.”
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ABOUT LRIS
The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.