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Theoretical physicists from Italy, Spain and Argentina propose a new mechanism for creating supermassive black holes from dark matter.
The galaxy halos could harbor a very dense core of dark matter, which could potentially mimic the effects of a central black hole, or possibly collapse to form one. Image credit: Sci-News.com.
Standard formation models imply that normal baryonic matter collapses under gravity to form black holes, which then grow over time.
A research team led by Dr Carlos Argüelles of the Universidad Nacional de La Plata and ICRANet investigated the potential existence of stable galactic nuclei made of dark matter and surrounded by a halo of dilute dark matter.
They found that the centers of these structures could become so concentrated that they could also collapse into supermassive black holes.
This could have happened much faster than other proposed formation mechanisms, and would have allowed supermassive black holes in the early Universe to form before the galaxies they inhabit, contrary to current understanding.
“This new formation scenario may offer a natural explanation of how supermassive black holes formed at the start of the Universe, without requiring prior star formation or without needing to invoke seed black holes with unrealistic accretion rates, ”said Dr Argüelles.
Another interesting consequence of the new model is that the critical mass for black hole collapse might not be reached for smaller dark matter halos, for example those surrounding some dwarf galaxies.
The researchers suggest that this could then leave smaller dwarf galaxies with a central core of dark matter rather than the expected black hole.
Such a dark matter core could still mimic the gravitational signatures of a conventional central black hole, while the outer dark matter halo could also explain the observed galaxy rotation curves.
“This model shows how dark matter halos could harbor dense concentrations at their centers, which can play a crucial role in helping to understand the formation of supermassive black holes,” said Dr Argüelles.
“Here we have proven for the first time that such distributions of nucleus-halo dark matter can indeed form in a cosmological setting and remain stable throughout the lifetime of the Universe.
“We hope that new studies will better understand the formation of supermassive black holes in the very early days of our Universe, as well as determine whether the centers of non-active galaxies, including our own Milky Way, can accommodate these dark dense . nuclei of matter. “
The team’s article was published in the Monthly notices from the Royal Astronomical Society.
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Carlos R. Arguelles et al. 2021. On the formation and stability of fermionic dark matter halos in a cosmological framework. MNRAS 502 (3): 4227-4246; doi: 10.1093 / mnras / staa3986
This article is based on a text provided by the Royal Astronomical Society.
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