This is one of a series of notes taken during the 2015 meeting of the AAS Division on Dynamical Astronomy, 3-7 May, at CalTech. An index to this series (all the papers presented at the meeting) is here.
Kelly Holley-Bockelmann (Vanderbilt)
Abstract
[None]
Notes
- How to bringBHs together: three phases
- Galaxy mergers sinkBHs through dynamical friction
- $\sim 10^5$ pc
- Sink closer via 3-body scattering
- Quinlan 1997
- dynamical friction no longer operating
- $\sim 10$ pc, $\sim 10^{10}$ yr(!?)
- Finally, GW complete the merger
- $\sim 10^{-5}$ pc
- Galaxy mergers sinkBHs through dynamical friction
- Problem: once loss coneis depleted by 3-body scattering, it can only be refilled by 2-body relaxation
- Merger stalls at $\sim 1$ pc
- hence the “final parsec problem”
- Begelman, Blandford, & Rees 1980, Makino 1997, Merritt & Milos 2005
- Merger stalls at $\sim 1$ pc
- Solution: galaxies are not idealized gas-free, stable, equilibrium systems!
- Mayer et al. 2007: galaxies have gas; gas drives theBHs closer
- drag(?)
- spiral wave torques
- problem: AGN feedback
- Ostriker,Binney, & Silk 1989: galaxies aretriaxial
- triaxiality introduces new mechanisms for phase space transport
- chaos
- Berczik et al. 2005
- gets you to grav radiation regime
- triaxiality introduces new mechanisms for phase space transport
- Khan,KHB,Berczik, and Just 2013: test limits of 3-body scattering
- N-body sims
- gas-poor, non-rotating, axisymmetric potential
- still takes too long (2.5 Gyr)
- found special orbits to fill loss cone
- because near BH the potential istriaxial
- even closer, is spherical
- $\rightarrow$ changes in shape are important
- because near BH the potential istriaxial
- add rotation $\rightarrow$ merger goes faster (yay)
- axisymmetric, counter-rotating: ~100 Myr
- but eccentricities very high
- axisymmetric, counter-rotating: ~100 Myr
- Mayer et al. 2007: galaxies have gas; gas drives theBHs closer