Supermassive Black Hole Binaries in AGNs

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Supermassive Black Hole Binaries in AGNs
KIAA-PKU Opening Symposium 06/29/2008

• Fukun Liu
• Astronomy Department, Peking University

• PKU Xue-Bing Wu, Xian Chen, Gang Zhao
• Oxford Univ. John Magorrian
• Albert Einstein Institute (AEI) Luciano
  Rezzolla

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Outline

• Brief introduction
• formation, expectation, evolution in dry and wet
  galaxy mergers, where to looking for
• SMBHBs in AGNs and its observations
• Post-merged BHs and recoil velocity
• Prospect and conclusions

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1?Introduction1.1? Formation mergers of
galaxies or globular clusters
Hierarchical galaxy formation in ?CDM cosmology
(Credit MPA)
Begelman, Blandford, Rees, 1980, Nat
SMBHBs at Sgr A? (Hansen Milosavljevic 2003)
NGC4472 (Maccorane et al, 2007, Nat)
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1.2?Expectation Gravitational wave
astronomyLaser Interferometer Space Antenna
(LISA) (Danzmann 2003)
LISA ??10-4-10-1 Hz (MBH?104 -107M?)
Measuring the change of distance
Pulsar Timing Array (PTA) (Lorimer 2005 Edwards
et al. 2006) very low frequency (VLF) with
pulsars ? ?10-9-10-5 Hz (MBH 107-1010 M?)
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1.3?Evolution in gas-poor mergers (dry merger)
SMBHB how to lose orbital angular momentum?

• Four stages of evolution (Begelman et al., 1980
  Quinlan 1996 Yu 2002)
• 1). Unbound a 10 pc
• Galactic dynamic friction
• 2). Bound 10 pca1pc
• Galactic dynamic friction
• Three body slingshot
• 3). Hard 0.1pca10-3pc
• ?a a/da/dt1010 yr
• Three body? Gas? poorly understood
• 4). GW dominated a10-3pc

Hard SMBHB how to lose angular momentum at
stages 3? final pc-scale problem
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1.4?Evolution in gas-rich mergers (wet mergers)

• The evolution of SMBHBs is different
• probably only three stages (e.g. for BH 2.6x106
  M?)
• 1). Unbound 50 Kpc ? a 40 pc
• Galactic dynamic friction
• two BHs embedded in a rotating gaseous disk of
  size a few 100 pc
• 2). interaction with gas disk and spherical
  accretion of gas a
• gas nuclear turbulent rotationally supported
  disk size 75 pc, scale height 40 pc
• rapid migration on a timescale 106yr
• 3). GW stage a ? 10-3 pc

Mayer et al. 2007, Sci. 316, 1874
Separation fo two SMBHs evolution with time
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1.5?Grand unification of galaxies and AGNs
SMBHB
Grav.
gas?center
?
Ultra-luminous infrared (ULIRGs)
sub-millimeter Galaxies (SMGs)
BHs accrete gas with Eddington accretion
rate?buried AGNs
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SMBHBs

• in non-active (nearby) galaxies
• by my student Xian Chen in this meeting
• in AGNs
• following the evolution of SMBHBs in galaxies

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2?SMBHBs in AGNs and its observations
2.1?Binary systems with large separation (a ?
kpc)

• Accretion of two BHs AGN binaries (luminous IR
  galaxies)
• e.g. NGC6240 (1.4 kpc, z0.0243, Komossa et al.
  2003)

• Image Spectra with Keck (Max et al. 2007, Sci.)
• BHs at centers of rotating nuclear disk
• young star clusters on the disks receding side

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• 2.2?Binary systems with separation a ? 0.1-1 pc

• Unperturbed disk standard thin (H/r LEdd
• BH Binary randomly inclined with respect to
  accretion disk

Quadruple contributions of the secondary to the
gravitational potential the precession of disk
tprec
twp
Warps and twists of inner disk by the secondary
(Ivanov et al. 1999)
transition radius tprec ? twp
BH spin axis reorientation due to
Bardeen-Peterson effect
Jet reorientation in luminous radio galaxies on

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X-shaped radio galaxies Jet reorientations due
to standard disk-binary interaction (Liu 2004)

• Winged radio galaxies (Hogbom Carlsson 1974,
  Capetti et al., 2002, Dennett-Thorpe et al. 2002)
• FRII radio galaxies 7
• Jet reorientation 106 yr
• No evidence for recent merger minor merger
• Wings aligned with the minor axis of the host
  galaxy

• Predications for X-shaped radio galaxies
• BH binary to coalesce
• Warped disk in AGNs double-peaked emission lines

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A clear gap in a standard thin disk (Lin
Papaloizou 1986, ArmitageNatarajan 2002)? q
(81?/8)? (H/r)2 ? 10-5
2.3?Binary systems with 0? a truncation of accretion disk at coalescence
(Liu, Wu, Cao, 2003)
Migration type II
tvis
Disk truncation
2Rtr103rG
decoupling tvis tGW
tgw
refilling tvis106 M8 yr
Migration GW radiation
SMBBHs coalescence
Removal of inner region 1) interruption of jet
formation in AGNs (Liu et al. 2003) 2) X-ray
afterglow (Milosavljevic Phinney, 2005)
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2.4?Binary systems in geometrically and optically
thick (e.g. slim disk) H/r 0.1 ( ?)

• A gap in the accretion disk for a binary
• q (81?/8)? (H/r)2 10-3
• accretion across the gap
• Density wave transport wavelike (Artymowicz 1994
  Escala et al. 2004, 2005 Dotti et al., 2006,
  Mayer et al. 2006 Hayasaki 2008)
• outwardto infinite distance
• inwards reflection between the inner boundary of
  accretion disk and the inner edge of gap

Outer Lindblad resonance
truncation of the inner disk region by binary BHs
in major merger (Artymowicz Lubow 1994
Milosavljevic Phinney, 2005, MacFadyen
Milosavljevic 2008 )
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• Double-double radio galaxies (DDRGs)
• Interruption of jet formation due to the removal
  of inner disk at SMBHB coalescence (Liu, Wu
  Cao 2003)

• DDRGs (Schoenmakers et al. 2000)
• Two pairs of well aligned radio lobes
• Interruption of jet formation 1 Myr
• Only FR II radio galaxies
• A subclass of giant radio galaxies

Predications co-existence of X-shaped radio
feature and double-lobes in a radio galaxy (Liu
2004)
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2.5? Binary systems in advection dominated
accretion flows (ADAF) H/r ? 1 ( ? ? 0.1 0.3)

• ADAFs optically thin, geometrically thick
• The interaction of SMBHBs and ADAFs is not well
  understood
• However, observationally very interesting
• Periodic optical and radio outbursts are reported
  in many BL Lac objects probably due to SMBHBs at
  center
• e.g. OJ 287 (Sillapaa et al. 1988 Liu Wu 2002
  etc), ON231 (Liu et al. 1995), Mkn421 (Liu et al.
  1997), AO 0235164 (Raiteri et al. 2001 Liu et
  al. 2006)
• BL Lac objects are beamed FRI low luminous radio
  galaxies which are probably powered by ADAFs
  (e.g. Ghisellini Celotti 2001)

• BL Lac object OJ287
• P11.64 yr
• double-peaked outbursts

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(Rezzolla et al. 2003, Rubio-Herra Lee 2005)
Torus global/local perturbation
BH
Harmonic QPOs in BL Lac object AO 0235164 (Liu
et al., 2006) thick disk p-mode oscillations?
Fundamental frequency ?s
From the databases at UMRAO NRAO at 4.8, 8,
14.5, 22 and 37 GHz
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2.6?Jet precession and its acceleration because
of the SMBHB evolution (Liu Chen 2007, ApJ)

• Jet precessions is the prototype of observational
  evidence for SMBHBs in AGNs (Begelman, Blandford,
  Rees 1980)
• Evolution of SMBHB on a viscous timescale (Type
  II migration) (Ivanov et al. 1998, 1999, Armitage
  Natarajan 2002, etc)
• Jet precedes on a timescale Ppre ? a? 104-107 yr
  (Begelman et al. 1980 Katz 1997 Romero et al.
  2000 Liu Chen 2007)

• Jet precession is accelerated due to binary
  evolution (Liu Chen 2007)

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Jet precessions in NGC1275 SMBHB evolution?

• From X-ray, radio emissions and H? line
  filaments, Dunn et al (2006) measuring the
  averaged jet precession timescale in NGC1275
• ancient?ghost Ppr2.27x108yr
• ghost?outer Ppr7.82x107yr
• Outer lobe?jet Ppr2.72x107yr

X-ray (left) and 330-MHz radio (right) (Dunn,
Fabian, and Sanders, 2006)

• From the observations, one can compute
• ancient?ghost?outer ? -2.55,
  15.2x107yr
• ghost?outer?jet ? -1.30,
  5.27x107yr

q?0.76, ?a?7.5x107yr, a1.46Kpc?0.80Kpc,
da/dt?-15.2 Km/s
BH mass MBH3.4x108M? (Wilman et al. 2005)
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3?Post-merged BHs recoil velocity

• Any asymmetry in the merging binary system leads
  to anisotropic gravitational radiation (Peres
  1962 Berkenstein 1973) ? carrying away momentum
  ? recoil velocity

• Schwarzschild SMBHBs due to the unequal masses
  (Fitchett 1983 Favata et al. 2004 Gonzalez et
  al. 2007 etc) vrecoil ? 176 km s-1
  at ? mM/(mM)2 0.195
• Kerr SMBHBs due to BH spins (Campanelli et al.
  2007 Pollney et al. 2007 etc) Vrecoil ? 3750
  km s-1

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Observational signatures due to impulsive kick

• Expectations
• IR afterglow due to shocks in truncated accretion
  disk in IR (Shields Bonning 2008 Schnittman
  Krolik 2008 Lippai et al. 2008)
• spatially offset and oscillating quasars (Madau
  Quataert 2004 Loeb 2007 Gualandris Merritt
  2008)
• prompt electromagnetic counterparts to the
  coalescence (Kocsis et al. 2008 Dotti et al.
  2006)
• ejection of quasars from host galaxies (Merritt
  et al. 2004)
• X-ray tails due to shocks of gas by recoiling
  SMBHs in elliptical galaxies (Devecchi et al.
  2008)
• broad emission lines offset from the narrow
  emission lines (Bonning et al. 2007 Komossa et
  al. 2008)
• Observations quasar SDSS J09272943 broad
  emission lines blueshifted relative to narrow
  emission lines with velocity v 2650 km
  s-1(Komossa et al. 2008)

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5?Prospects and conclusions

• SMBHBs are expected by the hierarchical galaxy
  formation model
• AGN binaries have been observed in a couple of
  merging galaxies but bound and hard SMBHBs have
  not yet been detected
• The interaction of SMBHBs and accretion gas would
  give rich observational signatures on the
  formation and evolution of SMBHBs in gas-rich
  systems
• The observation and identification of recoiling
  SMBHs is of great interests.
• Constraints on the distribution of massive binary
  BHs in normal galaxies would greatly help to
  solve the pc-scale problem.