Massive central objects affect both the structure and evolution of galactic nuclei. Adiabatic growth of black holes generates power-law central density profiles with slopes in the range 1.5 <∼ −d log p/d log r <∼ 2.5, in good agreement with the profiles observed in the nuclei of galaxies fainter than MV ≈ −20. However the shallow nuclear profiles of bright galaxies require a different explanation. Binary black holes are an inevitable result of galactic mergers, and the ejection of stars by a massive binary displaces a mass of order the binary’s own mass, creating a core or shallow power-law cusp. This model is at least crudely consistent with core sizes in bright galaxies. Uncertainties remain about the effectiveness of stellar- and gas-dynamical processes at inducing coalescence of binary black holes, and uncoalesced binaries may be common in low-density nuclei. Numerical N-body experiments are not well suited to probing the long-term evolution of black hole binaries due to spurious relaxation. (Refer to PDF file for exact formulas).
Date of creation, presentation, or exhibit
Department, Program, or Center
School of Physics and Astronomy (COS)
Merritt, David, "Single and binary black holes and their influence on nuclear structure" (2004). Accessed from
RIT – Main Campus