1 / 20

Bence Kocsis (CFA)

Gas Driven Supermassive Black Hole Binaries: periodic quasar variability and the gravitational wave background. Bence Kocsis (CFA). Einstein Symposium, 10/26/2009. Galaxies merge  ignite quasars  black holes merge AGN variability surveys and Pulsar Timing Arrays detects them.

carson
Download Presentation

Bence Kocsis (CFA)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Gas Driven Supermassive Black Hole Binaries: periodic quasar variability and thegravitational wave background Bence Kocsis (CFA) Einstein Symposium, 10/26/2009

  2. Galaxies merge  ignite quasars  black holes merge AGN variability surveys and Pulsar Timing Arrays detects them

  3. Evolution of binaries • Collisionless damping (~kpc; “dynamical friction”, “Landau damping”) • 3-body encounters with stars (~ 1 pc) • Gas driven migration (~0.1 pc, “Type II migration”) • Gravitational waves (~0.01 pc) Note: sub-parsec SMBH binaries ~ weeks – months orbital periods ~ 103 – 104 km/s velocity

  4. Evolution of binaries • Collisionless damping (~kpc; “dynamical friction”, “Landau damping”) • 3-body encounters with stars (~ 1 pc) • Gas driven migration (~0.1 pc, “Type II migration”) • Gravitational waves (~0.01 pc) Note: sub-parsec SMBH binaries ~ weeks – months orbital periods ~ 103 – 104 km/s velocity Number of binariesreduced at corresponding separation due to gas!

  5. Within the last pc • Thin gaseous disk • Disk aligns with binary plane (Bardeen & Peterson 1975, Ivanov et al. 1999) • Binary evacuates cavity(Artymowicz & Lubov 1994) • Viscous decay (“Type II migration”) • Secondary dominated • Disk dominated • Gravitational Wave driven evolution Cuadra et al. 2009; see also Ivanov et al. 1999; Armitage & Natarayan 2002, 2005; MacFadyen & Milosavljevic 2008;

  6. Within the last pc • Accretion Rate • Thin gaseous disk • Disk aligns with binary plane (Bardeen & Peterson 1975, Ivanov et al. 1999) • Binary evacuates cavity(Artymowicz & Lubov 1994) • Viscous decay (“Type II migration”) • Secondary dominated • Disk dominated • Gravitational Wave driven evolution Cuadra et al. 2009; see also Ivanov et al. 1999; Armitage & Natarayan 2002, 2005; MacFadyen & Milosavljevic 2008;

  7. Within the last pc • Residence Time • Thin gaseous disk • Disk aligns with binary plane (Bardeen & Peterson 1975, Ivanov et al. 1999) • Binary evacuates cavity(Artymowicz & Lubov 1994) • Viscous decay (“Type II migration”) • Secondary dominated • Disk dominated • Gravitational Wave driven evolution Haiman, Kocsis, Menou, 2009, ApJ, 700, 1952

  8. Within the last pc • Residence Time • Thin gaseous disk • Disk aligns with binary plane (Bardeen & Peterson 1975, Ivanov et al. 1999) • Binary evacuates cavity(Artymowicz & Lubov 1994) • Viscous decay (“Type II migration”) • Secondary dominated • Disk dominated • Gravitational Wave driven evolution Haiman, Kocsis, Menou, 2009, ApJ, 700, 1952

  9. Detecting Decaying binaries • Optimistic Assumptions: • binary is producing bright emission (~30% Ledd) • non-negligible fraction (~10%) of this emission is variable • clearly identifiable periodtvar~ torbit • in-spiraling binary = periodically variable quasar • Identifying such binaries statistically? • fraction of quasars with period tvar = (1+z) torb fvar = tres / tQ

  10. Requirements for an (optical) surveyfor finding periodic variable sources • Require: ≥ 100 sources @ tvar≤ 1 yr ≥ 5 sources @ tvar≤ 20 wk • Assume: • fEdd= 0.3 • fvar = 0.1 • tQ = 107 yr • Hopkins et al. QSOLF @ z=2 • Conclude: • wide survey best to probe GW-decay • disk physics at i~26.5 Haiman, Kocsis, Menou, 2009, ApJ, 700, 1952

  11. Pulsar Timing Arrays Pulsar Intensity Earth Time

  12. PPTA (Parkes pulsar timing array)‏ NanoGrav (north American nHz observatory for gravitational waves)‏ LEAP (large European array for pulsars)‏

  13. Millennium Run GW background for PTAs • Characteristic gravitational wave (GW) signal • Merger history  Millennium Run(Springel et al. 2005; Sesana et al. 2009) • “Residence time” at sub-pc scales  From our previous plot

  14. Gravitational Waves for PTAs Gas OFF Gas ON Kocsis & Sesana (2009) Unresolved background Contribution of individual sources Spectrum averaged over 1000 Monte Carlo realizations Total signal

  15. Summary • SMBH binaries, gas/GW driven dynamics • AGN surveys • Look for week-month year periodic variability • Look for spectral features~ several x 1,000 km/s • Pulsar Timing Arrays • Gas suppresses the stochastic background • Individually resolvable sources remain

  16. Statistics of resolvable sources basically unaffected Higher signal variance: impossible to characterize the slope of the background a priori

  17. Millennium Run GW background for PTAs • Characteristic gravitational wave (GW) signal • This depends on • Merger history  Millennium Run(Springel et al. 2005; Sesana et al. 2009) • “Residence time” at subparsec scales  From our previous plot

  18. SMBH Merger history • Millennium simulation (Springel et al. 2005) • N-body numerical simulation of halo hierarchy • Semi-analytical models for galaxy formation and evolution • We extract catalogs of merging galaxies and populate them with sensible MBH prescriptions

  19. Cartoon Model of Binary + Gas evolution • Gas cools and settles into a thin circumbinary disk • Disk aligned with binary orbital plane (Bardeen & Peterson 1975, Ivanov et al. 1999) • Torques from binary evacuate central cavity r ~ 2a(Artymowicz & Lubov 1994) • Orbit decays due to torques and viscosity, gas follows • Analogous to Type – II planetary migration • When local disk mass < binary mass  migration slows down • tGW becomes shorter than tvis when r ~ 100 RS

  20. Punctured disk

More Related