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Galactic Super Massive Binary Black Hole Mergers

Galactic Super Massive Binary Black Hole Mergers. Dr. Peter Berczik Astronomisches Rechen-Institut (ARI), Zentrum f ü r Astronomie Univ. Heidelberg, Germany. berczik@ ari.uni-heidelberg.de. Second RSDN meeting, 25-27 Nov. 2005, Hoher List, Germany. Collaborators:.

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Galactic Super Massive Binary Black Hole Mergers

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  1. Galactic Super Massive Binary Black Hole Mergers Dr. Peter Berczik Astronomisches Rechen-Institut (ARI), Zentrum für Astronomie Univ. Heidelberg, Germany berczik@ari.uni-heidelberg.de Second RSDN meeting, 25-27 Nov. 2005, Hoher List, Germany

  2. Collaborators: • David Merritt, Rochester Institute of Technology, NY, USA • Rainer Spurzem, ARI, Zentrum für Astronomie Univ. Heidelberg • Gabor Kupi, ARI, Zentrum für Astronomie Univ. Heidelberg • Stefan Harfst, Rochester Institute of Technology, NY, USA Grants: • AST-0206031, AST-0420920 & AST-0437519 from the NSF • NNG04GJ48G from NASA • HST-AR-09519.01-A from STScI • SFB-439 from the Deutsche Forschungsgemeinschaft Publications: • Berczik, Merritt & Spurzem, 2005, ApJ, 633, 680, [astro-ph/0507260] • Berczik, Merritt & Spurzem, in prep…

  3. Galaxy Collisions:

  4. BH’s in galaxies (MW - Sgr A*):

  5. Galaxy Collisions ≈ BH’s collisions: Multiple Massive Black Holes NGC6240 strong ongoing merger…

  6. Future Observations: Gravitational Wave Detection - LISA • Two of the strongest potential sources in the • low-frequency (LISA) regime are: • Coalescence of binary supermassive black holes • Extreme-mass-ratio inspiral into supermassive black holes

  7. Some of the previous works: • Milosavljevich M. & Merritt D., 2001, ApJ, 563, 34 • Hemsendorf M., Sigurdsson S. & Spurzem R., 2002, ApJ, 581, 1256 • Chatterjee P., Hernquist L. & Loeb A., 2003, ApJ, 592, 32 • Makino J. & Funato Y., 2004, ApJ, 602, 93 • Laun F. & Merritt D., 2004, [astro-ph/0408029] • Szell A., Merritt D. & Seppo M., 2005, [astro-ph/0502198] Dynamical Modeling Methods: Direct N-body method: • As much as possible accurate… • Symmetry of the problem is irrelevant… • (-) Very compute intensive!!!

  8. Basic idea of the N-body code:

  9. Our own GRAPE+N-body1 parallel code: 4th order Hermite scheme Hierarchical Block Time Steps

  10. GRAPE = GRAvity PipE ~N ~N^2

  11. GRAPE = GRAvity PipE – more detail…

  12. GRAPE6a PCI board GRAPE6a - PCI Board for PC-Clusters, recent development of the University of Tokyo ~128 Gflops for a price ~5K USD Memory for N, up to 128K particles

  13. RIT & ARI 32 node GRAPE6a clusters • 32 dual-Xeon 3.0 GHz nodes • 32 GRAPE6a • 14 TB RAID • Infiniband switch (10 Gb/s) • Speed: ~4 Tflops • N up to 4M • Cost: ~500K USD • Funding: NSF/NASA/RIT • 32 dual-Xeon 3.2 GHz nodes • 32 GRAPE6a • 32 FPGA • 7 TB RAID • Dual port Infiniband switch (20 Gb/s) • Speed: ~4 Tflops • N up to 4M • Cost: ~350K EUR • Funding: Vwagen/BW/ARI

  14. RIT & ARI 32 node GRAPE6a clusters

  15. Parallel PP on GRAPE6a cluster N Nact N/Np

  16. Parallel PP on GRAPE6a cluster

  17. Parallel PP on GRAPE6a cluster

  18. Parallel PP on GRAPE6a cluster

  19. Parallel PP on GRAPE6a cluster

  20. Initial Conditions - I: Z Two equal-mass black holes near center of Plummer-model galaxy Y X

  21. Some Theory: N-body Integration of Binary Black Hole Dynamical Evolution star Example: loss-cone around a binary black hole. Stars scattered into the binary are ejected via the gravitational slingshot. The binary responds by shrinking. θ Full loss-cone Diffuse regime binary black hole In a real galaxy, the shrinking rate (d/dt)(1/a) would be limited by the rate of diffusion of stars into the loss cone.

  22. Results – I (Plummer):

  23. Results – I (Plummer):

  24. Initial Conditions - II: Z Two equal-mass black holes near center of King-model (W0=6) galaxy Y X

  25. Results – II (King):

  26. Results – I (Plummer) + II (King):

  27. Double check of the Results:

  28. Double check of the Results:

  29. BH collisions? ??? d ~10*R_BH If we scaled up our numerical results, for the typical galaxy bulge (~10^9 Mo & ~3 kpc: 10 Gyr = 130) we see that the BH’s separation never come closer ~1 – 0.1 pc… For the typical BH’s mass (10^6 Mo) the “gravitational merging” regime start with ~10^-6 pc!!!

  30. Possible way of “solution”: • Initial data… • No equilibrium… • Higher initial eccentricity… • New code: ε=0 • regularization (CHAIN - ?, KS - ?)… • Larger direct N simulations: • AC neighbor scheme… • N-body + GAS (SPH) • Hardware solution for SPH calculations (FPGA)

  31. Conclusions: • First large direct N ~1M parallel GRAPE6a cluster simulations… • The BBH decay rate is N dependent! ~400K – 1M particle is already enough to have a near “diffuse” regime… • The initial rotation of the host galaxy is very important for the BBH orbital evolution. For larger rotation we see the clear “fixation” of decay rate… • Some of the highly rotating models can produce the BBH with a very high eccentricity e~1. Possible source of the low frequency GW (LISA)… Thank you for attention...

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