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Search for Binary Black Holes in Galactic Nuclei

Search for Binary Black Holes in Galactic Nuclei. Hiroshi SUDOU (Gifu Univ., Japan) sudou@gifu-u.ac.jp. Outline. Introduction to Binary (supermassive) Black Hole (BBH) Possible evidence for BBHs Ideas for KVN/EAVN observations Prospects for VSOP-2. Evolution. Basic scenario:

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Search for Binary Black Holes in Galactic Nuclei

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  1. Search for Binary Black Holesin Galactic Nuclei Hiroshi SUDOU (Gifu Univ., Japan) sudou@gifu-u.ac.jp EAVN Workshop, Seoul, 2009 March 19

  2. Outline • Introduction to Binary (supermassive) Black Hole (BBH) • Possible evidence for BBHs • Ideas for KVN/EAVN observations • Prospects for VSOP-2

  3. Evolution Basic scenario: 1) a galaxy have a SMBH 2) galaxy merging often occurs 3) merged galaxy should have two SMBH in its center 4) two BH forms BBH system 5) they finally merge into one with gravitation wave burst Dynamical Friction Gravitational Wave Begelman et al. 1980

  4. Good Target for VLBI • Lifetime of BBH can be the longest between DF phase and GW phase • The most observable examples of BBHs will have Separation ～　0.01 - 1 pc (20 - 2000 micro-as @ 100Mpc) Orbital period ～ 1 – 100 yr

  5. NLR Schematic View of BBH Jet 10-100pc Torus BLR 0.1pc BH Accretion Disk 0.1pc 10pc Detection of orbital motion of BH is direct evidence for BBH !

  6. Possible Evidence (1)Periodic Flux Variations OJ287 (Sillanpaa et al. 1998)

  7. Possible Evidence(2)Jet shape Twin jet (3C75) Precession jet (1928+738) Owen et al. 1985 Yokosawa and Inoue 1985 Roos et al. 1993

  8. Possible Evidence (3)Double AGN core Chandra VLBA r ~ 10 pc r ~ 1 kpc Komossa et al. 2003 Mines et al. 2004

  9. Detecting BBH with VLBI Combination of these methods is very important

  10. Periodic flare due to BBH • How to find characteristic variation due to BBH ? What is variation mechanism ? • Theoretical study / simulations Hayasaki et al. 2006 Multi-frequency observations are important

  11. Flux monitoring with KVN • Searching for periodic variation with period of < a few yr • KVN is suitable for this project • sensitive mm-wave (less jet contamination) • multi-frequency (22-120 GHz) • Combination with other wavelength • Note: X-ray all-sky monitoring facility MAXI will be on board ISS in 2009 Based on monitoring results, we can go to further BBH search

  12. Problems of this idea • Clarify importance of multi radio-frequency • What is flaring mechanism at mm-wavelength ? • More theoretical study must be needed • Source selection criteria (merging or merged galaxy ? Sensitivity limited ?) • Probability to detect orbiting BHs • GW emitting phase would be very short (< 104 yr) compared with AGN timescale (108 yr ?)  More detailed discussion needed

  13. BBH is important target for VSOP-2 Longest baseline: 25,000 km Frequency: 8, 22, and 43 GHz Spatial resolution: 40 micro-arcsec @ 43G Launch: FY2012 High spatial resolution is essential, 40 micro-as  0.02 pc @ 100Mpc for detecting harder BBHs emitting gravitation wave!

  14. Summary • BBHs with r~0.1pc, P~10 yr would be most observable examples • Proposing idea of flux monitoring with KVN, but needed more discussion • Based on monitoring results, VSOP-2 could confirm the presence of BBH emitting gravitation wave Hoping to much friendly collaborate with East-Asia people !

  15. Possible evidence (x) Core motion • @8GHz Radio Galaxy 3C66B 1 2 4 6 5 3 8 GHz 50 micoro-as α δ Further observations are needed !

  16. MAXI • Monitor of all-sky X-ray image • 0.5 – 30 keV • Position accuracy ~ 6 arcmin • Every 90 min (1 orbit), all-sky image will be obtained • 1000 X-ray source is expected to be detected, including AGN, X-ray binary, etc

  17. Orbital period The most observable examples of BBHs will have P ～ 1 - 100 yr

  18. Comparison between Binary Pulsar and BBH

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