1. Black hole binary mergers: recent developments in numerical relativity First-term presentation By Nikos Fanidakis Supervisors: Carlton Baugh, Shaun Cole, Carlos Frenk 13/12/2007

2. Outline Brief introduction to gravitational waves Black hole (BH) binary mergers in numerical relativity Astrophysical implications: recoil kicks Discussion – conclusions

3. 3 Quantum Fluctuations in the Early Universe Merging super-massive black holes (SMBHs) at galactic cores Capture of BHs and compact stars by SMBH Merging binary NSs and BHs in distant galaxies NS quakes and magnetars Gravitational wave radiation  Gravitational Waves: ripples of space-time curvature propagating at the speed of light.  Gravitational wave sources: any source with nonzero quadrupole moment. Amplitude h ≈ (GM/Rc 2 )(R/D) =10 -23 -10 -21

4. BH mergers in numerical relativity: 1964-2005 Image courtesy: Kip Thorne  BHs are strong sources of gravitational waves!  A merge of two equal mass BHs releases ~ 10 56 ergs/s  Accurate gravitational waveforms are essential for LISA  First attempt by Hahn – Lindquist (1964): inspiral (!) → merger(??) → ringdown (!) ?

5. BH mergers in numerical relativity: 2005-2007 time amplitude inspiral merger ringdown Baker et al. 2006  1. The technique:  “3+1” decomposition 3-d hypersurfaces.  Evolution of hypersurface through time using 17 nonlinear, coupled differential eqns!  2. The breakthrough (Baker et al. 2006):  Fixed “puncture” representation of the BH  Comoving coordinates

6. Astrophysical implications: recoil kicks Centrella et al. 2007  Asymmetric BH mergers impart a recoil kick to the final remnant (ejection from host structure?)  Unequal-mass BH merger simulation (Gonzalez et al. 2007): o Initial binary: m 1 =0.36m 2 u kick ~ 176 km/s  Highly-spinning BH merger simulation (Herrmann et. 2007): o Initial binary: equal-mass BHs with anti-aligned equal spins u kick =475 km/s M-σ relation constraint ≈ 500 km/s  If spin not perpendicular to orbital plane u kick up to 2000 km/s (Campanelli et al. 2007)

7. Discussion – conclusions known