Search for

Binary Black Holesin Galactic Nuclei

Hiroshi SUDOU(Gifu Univ., Japan)sudou@gifu-u.ac.jp

EAVN Workshop, Seoul, 2009 March 19

Outline Introduction to Binary (supermassive)

Black Hole (BBH) Possible evidence for BBHs Ideas for KVN/EAVN observations Prospects for VSOP-2

Begelman et al. 1980

Evolution

Dynamical Friction

Gravitational Wave

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

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

Schematic View of BBH NLR

BLR

Accretion Disk

Jet

Torus

BH

10pc0.1pc

0.1pc

10-100pc

Detection of orbital motion of BH is direct evidence for BBH !

Possible Evidence (1)Periodic Flux Variations

OJ287 (Sillanpaa et al. 1998)

Possible Evidence(2)Jet shape

Roos et al. 1993Owen et al. 1985Yokosawa and Inoue 1985

Twin jet (3C75) Precession jet (1928+738)

Possible Evidence (3)Double AGN core

Komossa et al. 2003 Mines et al. 2004

r ~ 1 kpc

r ~ 10 pc

Chandra VLBA

Detecting BBH with VLBI r [pc] P [yr] Phenonema Detection Methods facility

< 0.001 <1 Gravitationalwave

Pulsar timing SKA ?

0.01 1 Double core High spatial resolution imaging

VSOP-2

0.1 10 Core motion VLBI astrometry VERA/VLBA

Periodic flare Flux monitoring KVN

>1 >1000 Wiggling jet Sensitive imaging EAVN/VLBA

Combination of these methods is very important

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

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

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

BBH is important target for VSOP-2

Longest baseline: 25,000 kmFrequency: 8, 22, and 43 GHzSpatial resolution: 40 micro-arcsec @ 43GLaunch: FY2012

High spatial resolution is essential, 40 micro-as 0.02 pc @ 100Mpc for detecting harder BBHs emitting gravitation wave!

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 waveHoping to much friendly collaborate with East-Asia people !

Possible evidence (x) Core motion

α

δ

12

3

4

56

@8GHz

8 GHz 50 micoro-as

Radio Galaxy 3C66B

Further observations are needed !

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

0.010.1

110

1001000

10000100000

0.0001 0.001 0.01 0.1 1 10

r [pc]

P [y

r] 10̂ 7Msolar10̂ 8Msolar10̂ 9Msolar

Orbital period

yr10cm10

r502/1

solor8

2/3

17

MMP

The most observable examples of BBHs will have P ～ 1 - 100 yr

Comparison between Binary Pulsar and BBH

Binary Pulsar BBH

Object Nutron Star SMBH

Mass 1 Msolar 10^8 Msolar

Separation 10^11cm 10^17 cm

Period 3days 50yrs

GW frequency kHz mHz