Supermassive black holes are exotic astrophysical objects harbored at the centers of galaxies. Their masses can reach 1 million to 1 billion times larger than our sun, and their gravitational force is so strong that even light cannot escape; hence the name “black” holes.
Dark matter is a mysterious form of matter that lurks in galaxies and clusters of galaxies. It gives a strong gravitational pull but emits no light, so it is known as “dark.”
Now a new theoretical study has linked the “black” and the “dark” together.
A group of astrophysicists, led by Dr. Carlos Argüelles of the Universidad Nacional de La Plata and ICRANet, investigated the potential existence of galactic cores formed from dark matter.
They found that the centers of dark matter cores surrounded by diluted dark matter haloes could become so dense that they may collapse into supermassive black holes.
Standard black hole formation models involve baryonic matter (normal atomic matter) collapsing under gravity to become black holes.
The new study suggests that dark matter black holes could have happened much more quickly than in the standard model and would have allowed supermassive black holes to form before their host galaxies in the early universe, 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,” Argüelles said in a statement.
The new model also indicates an intriguing phenomenon: Smaller dark matter haloes may not have enough mass to reach the critical mass for collapse into a black hole. The team suggested that this situation might leave smaller dwarf galaxies with a central nucleus made of dark matter rather than a black hole.
Such a dark matter core could still mimic the gravitational signatures of a typical central black hole, while the outer dark matter halo could 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,” 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 published their paper in the Monthly Notices of the Royal Astronomical Society.