Theoretical physicists from Italy, Spain and Argentina propose a new mechanism for the creation of supermassive black holes from dark matter.
Standard formation models involve normal baryonic matter collapsing 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 cores made of dark matter, and surrounded by a diluted dark matter halo.
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 more quickly 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 for how supermassive black holes formed in the early Universe, without requiring prior star formation or needing to invoke seed black holes with unrealistic accretion rates,” Dr. Argüelles said.
Another intriguing consequence of the new model is that the critical mass for collapse into a black hole might not be reached for smaller dark matter halos, for example those surrounding some dwarf galaxies.
The researchers suggest that this then might leave smaller dwarf galaxies with a central dark matter nucleus rather than the expected black hole.
Such a dark matter core could still mimic the gravitational signatures of a conventional central black hole, whilst the dark matter outer halo could also explain the observed galaxy rotation curves.
“This model shows how dark matter haloes could harbour dense concentrations at their centers, which may play a crucial role in helping to understand the formation of supermassive black holes,” Dr. Argüelles said.
“Here we’ve proven for the first time that such core-halo dark matter distributions can indeed form in a cosmological framework, and remain stable for the lifetime of the Universe.”
“We hope that further studies will shed more light on supermassive black hole formation in the very earliest days of our Universe, as well as investigating whether the centers of non-active galaxies, including our own Milky Way, may play host to these dense dark matter cores.”
The team’s paper was published in the Monthly Notices of the Royal Astronomical Society.
Carlos R. Argüelles et al. 2021. On the formation and stability of fermionic dark matter haloes in a cosmological framework. MNRAS 502 (3): 4227-4246; doi: 10.1093/mnras/staa3986
This article is based on text provided by the Royal Astronomical Society.