The newly discovered black hole resides in the hyperluminous galaxy GN-z11 with a redshift of 11 and may have originated from a star-mass seed with redshifts of 12 to 15.
GN-z11 is a young but moderately massive galaxy located in the constellation Ursa Major.
First discovered in 2016, this galaxy is estimated to date from when the Universe was only 420 million years old, or 3% of its current age.
GN-z11 is about 25 times smaller than our Milky Way and has only 1% of the mass of our Galaxy in stars.
Surprisingly, according to the new study, the galaxy hosts a black hole of about 1.6 million solar masses.
Multiple theories have been proposed to describe the formation of black hole seeds in the early Universe and to explain the emergence of very massive black holes observed to be already present at redshifts z=6-7.5, said Professor Roberto Maiolino and colleagues from the University of Cambridge. .
Black holes resulting from the direct collapse of primordial clouds (probably preceded by the formation of a supermassive star) into seeds with masses between 10,000 and one million solar masses — so-called direct collapse black holes — are one of the most frequently invoked models.
However, other models also account for the rapid mergers of stars and black holes in dense nuclear star clusters, as well as accretion on Population III black hole seeds or even ordinary stellar remnants.
Super-Eddington’s accretion was also considered a possibility, they added.
However, none of these scenarios has been adequately tested so far, as they required the observation of black holes with higher redshift (z > 10) and lower masses (less than 10 million solar masses), which was impossible until Advent of the NASA/ESA/CSA James Webb Space Telescope.
In their study, Professor Maiolino and co-authors performed an in-depth analysis of the spectrum of GN-z11.
Initially detected with Hubble, this is the brightest galaxy with redshifts greater than 10 in all of the Hubble fields (including the entirety of the CANDELS and Frontier Fields), they said.
Being three times more luminous than the characteristic luminosity of galaxies at z=7, when fueled mainly by star formation, the implied density of luminous galaxies would be difficult to reconcile with many models of galaxy formation.
Astronomers analyzed spectroscopic data obtained with Webbs Near-Infrared Spectrograph (NIRSpec) as part of the JADES survey.
Analysis of the NIRCam images revealed that the galaxy is dominated by an active galactic nucleus (AGN).
The spectral features of GN-z11 indicate that, in addition to star formation, the galaxy also harbors an accreting black hole, the authors said.
We do not exclude a contribution from extreme stellar populations, however, Wolf-Rayet stars alone cannot explain many of the spectral properties.
GN-z11 is the first of the high-redshift hyperluminous galaxies to be spectroscopically confirmed, they added.
The AGN scenario revealed by our analysis provides a natural explanation for GN-z11’s exceptional luminosity.
If this is representative of the larger class of bright galaxies discovered at high redshifts by Webb, then it would greatly ease the tension with models and simulations and could suggest a stronger role for AGN in the reionization of the Universe.
Robert Maiolino et al. 2023. A small and vigorous black hole in the early Universe. arXiv: 2305.12492
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