Black hole binary mergers: recent developments in numerical relativity

First-term presentation

By Nikos FanidakisSupervisors: Carlton Baugh, Shaun Cole, Carlos Frenk

13/12/2007

Black hole binary mergers: recent developments in numerical relativity

First-term presentation

By Nikos FanidakisSupervisors: Carlton Baugh, Shaun Cole, Carlos Frenk

13/12/2007

Outline

• Brief introduction to gravitational waves • Black hole (BH) binary mergers in numerical

relativity• Astrophysical implications: recoil kicks• Discussion – conclusions

3

Quantum Fluctuations in the Early UniverseMerging 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

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 ~1056

ergs/s Accurate gravitational

waveforms are essential for LISA

First attempt by Hahn – Lindquist (1964): inspiral (!) → merger(??) → ringdown (!)?

BH mergers in numerical relativity: 2005-2007

time

ampl

itu

de

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

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: m1=0.36m2

ukick ~176 km/s Highly-spinning BH merger

simulation (Herrmann et. 2007): o Initial binary: equal-mass BHs with

anti-aligned equal spins

ukick =475 km/s

M-σ relation constraint ≈ 500 km/s If spin not perpendicular to orbital

plane ukick up to 2000 km/s (Campanelli et al. 2007)

Discussion – conclusions

known