Turbulent disk of gas swirling around a black hole. Credit: NASA’s Goddard Space Flight Center / Jeremy Schnittman
A new theoretical study has proposed a new mechanism for creating supermassive black holes from dark matter. The international team finds that instead of the conventional formation scenarios with ‘normal’ matter, supermassive black holes can instead arise directly from dark matter in areas of high density in the centers of galaxies. The result has important implications for cosmology in the early Universe and has been published in Monthly Communications from the Royal Astronomical Society
Exactly how supermassive black holes were initially formed is one of the biggest problems in the study of the evolution of galaxies today. Supermassive black holes have been around 800 million years after the Big Bang, and how they grew so fast remains unexplained.
Standard models of formation include normal baryonic matter – the atoms and elements that make up stars, planets, and all visible objects – that collapse under gravity to form black holes, which then grow over time. However, the new work explores the potential existence of stable galactic nuclei made of dark matter and surrounded by a dilute dark matter halo, finding that the centers of these structures could become so concentrated that they could also collapse into supermassive. black holes, once a critical point. threshold has been reached.
Artist’s impression of a spiral galaxy embedded in a larger distribution of invisible dark matter, known as a dark matter halo (colored blue). Studies of the formation of dark matter halos have suggested that each halo may harbor a very dense dark matter nucleus, possibly mimicking the effects of a central black hole, or eventually collapsing to form one. Credit: ESO / L. Calçada
According to the model, this could have happened much faster than other proposed formation mechanisms and supermassive black holes in the early Universe could have formed before the galaxies in which they live, contrary to current views.
Carlos R. Argüelles, the researcher at Universidad Nacional de La Plata and ICRANet who led the study, notes: “This new formation scenario may provide a natural explanation for how supermassive black holes formed in the early Universe, without prior star formation. is needed. evoke black holes with unrealistic growth rates. “
Another intriguing consequence of the new model is that the critical mass for collapse into one black hole may not be achieved for smaller dark matter halos, such as those around some dwarf galaxies. The authors suggest this could then leave smaller dwarf galaxies with a central dark matter nucleus in place of the expected black hole. Such a dark matter nucleus could still mimic the gravitational signatures of a conventional central black hole, while the outer halo of dark matter could also explain the observed galaxy rotation curves.
“This model shows how dark matter halos can harbor dense concentrations in their centers, which may play a critical role in helping us understand supermassive black hole formation,” added Carlos.
“Here we have proven for the first time that such distributions of dark matter between the nucleus and the halo can indeed form in a cosmological framework and remain stable over the lifetime of the Universe.”
The authors hope that further studies will shed more light on the formation of supermassive black holes in the very first days of our Universe, as well as investigate whether the centers of inactive galaxies, including our own Milky Way, can host these dense dark matter nuclei.
Reference: “About the formation and stability of fermionic dark matter halos in a cosmological framework” by Carlos R Argüelles, Manuel I Díaz, Andreas Krut and Rafael Yunis, December 31, 2020, Monthly Communications from the Royal Astronomical Society
DOI: 10.1093 / mnras / staa3986