Three supermassive black holes in a distant-and therefore very old-galaxy offer a glimpse into how black holes merged and grew in the early universe
An AI-generated visualisation of a distant galaxy, containing besides dust, gas and young stars three massive, active black holes (black spheres, not to scale) with bright accretion disks. Other distant galaxies are shown in the background, and few stars in the foreground.
© MPE (generated with AI)
containing besides dust, gas and young stars three massive, active black holes (black spheres, not to scale) with bright accretion disks. Other distant galaxies are shown in the background,
and few stars in the foreground.
To the Point
Three Black Holes Discovered in a Galaxy: For the first time, researchers have discovered three supermassive black holes in a galaxy (J0148-4214), each of which is actively accreting matter from its surroundings. Their masses range from a few to about 80 million solar masses. Two of the black holes are located closely together at the center of the galaxy, while a third is situated farther out.
Detection method: The discovery was made possible by spatially resolved spectroscopy using an instrument aboard the James Webb Space Telescope.
Black hole growth: The findings suggest that mergers and interactions in the early universe may have contributed to the rapid growth of supermassive black holes.
An international team of astronomers led by the Max Planck Institute for Extraterrestrial Physics has identified three actively accreting supermassive black holes in the galaxy J0148-4214. These are black holes into which matter is falling from an accretion disk surrounding them. The galaxy is located more than 12.5 billion light-years from Earth. At this distance, the expansion of space itself becomes apparent. The galaxy therefore appears to be moving away from us, causing the light received from the galaxy to shift toward longer wavelengths, resulting in a so-called redshift of z=5.02. Using that redshift, the researchers calculated the galaxy’s enormous distance. It is so far away that its light has traveled for 12.5 billion years. We are therefore seeing the galaxy as it appeared only about 1.2 billion years after the Big Bang.
“This is the first evidence of three active black holes in a single galaxy in the distant Universe,” says Hannah Übler, research group leader at MPE and lead author of the study. Two of them are located in the galactic center and are separated by only 620 light-years in projection. A third black hole is located in the outer region of the galaxy, at a distance of approximately 5500 light-years from the centre. “It suggests that processes in the early Universe were efficient at bringing massive black holes together, setting the stage for the massive black hole mergers we expect to detect with future gravitational wave observatories”, says Übler. This is because theories of galaxy evolution-based on observations-suggest that, early in the history of the universe, galaxies came very close to one another and merged. In the process, also the black holes at their centers merged and gave rise to black holes with even greater masses at the centers of the merged galaxies.
Hydrogen emission as a tracer
The researchers identified the black holes through their spectral fingerprints: the signatures of hydrogen atoms moving at high velocity in the gravitational potential of the black holes. In the central region, the spectrum exhibits a complex structure best explained by two black holes in close proximity. To disentangle the two central sources, the team applied spectro-astrometry, a technique that precisely measures spatial shifts in line emission across the galaxy. This made it possible to determine the positions of the black holes, even though they cannot be spatially resolved as separate point sources. A third black hole was detected in the outer region.
Masses and growth
The analysis yields black hole masses of approximately 80 million, 0.6 million, and 2 million suns. The most massive black hole is accreting at a lower rate than the nearby black hole with a mass of 0.6 million suns, which is actively feeding and even exceeding the maximum accretion rate predicted by basic theories of black hole growth (the Eddington limit).
“The JWST data allowed us not only to identify the three black holes, but also to estimate their masses, accretion rates, and the stellar mass of the galaxy,” says Dr. Giovanni Mazzolari, second author of the study and researcher at MPE. “We find a total stellar mass of about 1.3 billion suns, and the black holes represent a significant fraction of that.”
The central black hole pair is expected to merge within the next few hundred million years. “These results are extremely exciting,”, adds Roberto Maiolino, professor at the University of Cambridge and co-author of the study. “They suggest that black hole merging may be an additional, fast route for their rapid growth in the early Universe.”
The third black hole, located off-nucleus, may be the remnant of a previous merger, being displaced from the centre by a gravitational recoil kick, or may currently be migrating inward.
Implications for research
These observations demonstrate that integral field spectroscopy is an important tool for identifying multiple active black holes in distant galaxies. Without the spatially resolved information provided by NIRSpec-IFS, only one of the three black holes would likely have been detected.
