New study uses self-interacting dark matter to solve the final parsec problem

A recent study by Canadian scientists proposes a solution to the final parsec problem in supermassive black hole (SMBH) mergers by introducing the concept of self-interacting dark matter (SIDM). The final parsec problem occurs when two SMBHs, after merging galaxies, stall at a distance of 1 parsec due to gravitational wave emission and dynamical friction. The researchers suggest that SIDM, a hypothetical form of dark matter that interacts through an unknown force, could facilitate the merging process by altering the density and velocity of dark matter around the SMBHs. Their calculations indicate that an optimal interaction cross-section for dark matter particles is between 2.5 and 25 cm²/g, allowing sufficient interactions to reduce dynamical friction without dispersing the dark matter too much. Additionally, the velocity of SIDM particles must be optimal, influenced by the mass of the force carrier mediating their interactions. The study's findings align with gravitational wave data observed by the Pulsar Timing Array, suggesting that SIDM could lead to weaker gravitational waves at low frequencies. This research not only addresses the final parsec problem but also opens avenues for constraining dark matter models through gravitational wave emissions. The team plans to refine their model and conduct numerical simulations to further explore the dynamics of dark matter in the context of SMBH mergers.