活动星系核统一模型和超大质量黑洞的形成与增长

张双南

清华大学物理系和天体物理中心

科学院高能所粒子天体物理重点实验室

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Emission Line Spectra from Seyfert AGNs

Broad emission lines from Type-I Seyfert AGN

Narrow emission lines from Type-II Seyfert AGN

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Unification scheme for type-I and type-II AGNs

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Investigation of the obscuring circumnuclear torus in the active galaxy Mrk231: Kloeckner et al., Nature, 2003

The inferred model of the nuclear torus. The molecular material moves from top right to bottom left (northwest to southeast). Virial estimates of the central mass concentration give (7.2±3.8) x107 solar masses.

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• Sky deep surveys of Chandra and HST show that the fraction of type II AGN is decreasing with the hard X-ray luminosity.

•This indicates a breakdown of the ‘strong’ unification model where the covering factor H/Ri is independent of luminosity and redshift.

•This has been taken as the evidence of evolution of torus geometry

•Hasinger et al 2003 •Similar correlation has

been found by Steffen

et al. (2003). Sazonov &

Revnivtsev (2004),

Wang & Zhang (2004)

in other samples of

AGNs

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Anisotropy of X-ray emission from AGNs

• In all previous studies, it has been assumed implicitly that

• However, if the X-rays originate from the accretion disk surrounding the black hole, the observed apparent X-ray luminosity is related to its intrinsic luminosity by:

• Then for a given X-ray luminosity, randomly oriented AGNs will have apparent luminosity distribution:

)unabsorbed(4 2XLX FDL

AGNs I) (Type on-facefor 0

intrinsic)())cos(21(3

1)cos( 0,,

XX LL

[0,1] ddistributeuniformly is )sin(

)121(1)( 22

x

xxxf

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The inclination angle effect

Data from

Ueda et al. 2003

Zhang, 2005, ApJ, 618, L79

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The inclination angle effect on type-II AGN fraction

Zhang, 2005, ApJ, 618, L79

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考虑相对论效应对流强的修正

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考虑相对论效应对光度的修正

Better agreement than

non-relativistic model

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考虑相对论效应对光度的修正

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考虑相对论效应对能谱的修正

a=0.998 倾角 : 5 40 85 α : 0.89 0.85 0.75 (0.01)

Sy 2 spectra are harder than

Sy 1 spectra for Kerr BHs

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Anisotropy of inverse Compton scattering in corona

Maraschi & Haardt 1997

θ=0o

θ=60o

Disk kT=50 eV

Disk kT=100 eV

Higher inclination for

Softer spectrum!

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A.Malizia ApJ 2003 589 L17

04.003.092.0~

06.004.075.0~

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Inclination angle dependence of 2-10 keV spectral index

Zdziarski et al. 2000Anisotropy of inverse Compton scattering in spherical corona

Relativistic effects

(Disk origin in 2-10 keV)

Averaged Sy I index

Sy II index

Malizia et al. 2003

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Implications of this TAXI model

• TAXI model: Torus of Antonucci with X-ray Inclination-angle effects– X-rays are produced primarily in accretion disk, but not in

extended and near-spherical corona- Many similarities in X-ray variabilities between X-ray binaries

and AGNs suggest disk origin- Several theoretical models suggest viable mechanisms for X-ray

production from AGN disks, e.g., magnetic reconnection (like in the Sun), magnetic turbulent Comptonization

- Lack of broad Fe-K-alpha emission lines– Accretion disk and the torus are co-aligned with each other

- Consistent with the model of Krolik and Begelman (1988) in which the torus feeds the black hole.

• Question to be answered: How does the torus form the accretion disk surrounding the black hole?

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Important correlations of SMBH mass with properties of galactic bulge

Stellar dynamics

Maser disk dynamics

Ionized gas dynamics

Black holes grow together with their host bulges.

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No SMBH in M33? Merritt, et al, 2001, Science

•The M33 galaxy•850 kpc •spiral (disk) galaxy•with nuclear star cluster

•expected to host a BH•But no bulge

•No sharp increase of either V or towards the center of the galaxy

•Mass of the BH: < 3103 M⊙

BH grow together only with their host bulges, not with their disks.

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Unstable by design: Siemiginowska and Elvis, Nature, 1999

• Lower stable branch: viscous heating balanced by cooling (BB radiation)

• Higher stable branch: viscous heating balanced by cooling (thermal Bremsstralung radiation)

• Middle unstable branch: UV photons strongly absorbed by hydrogen (ionization), cooling inefficient.

– Increate accretion rate

- Increase UV absorption

– Jumps between lower and higher branches

Positive slope: stable diskNegative slope: unstable disk

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Advantages of the instability model

• Previous problem for quasars– High luminosity high accretion rate

- Fuel run out quickly many dead quasars in nearby galaxies: not found

• New understanding– High luminosity implies the quasar disks cannot be in

the lower branch– Irradiation of the disk insufficient to keep it in the

higher branch permanently- Active quasars are those in the higher branch

temporarily, due to irradiation instability

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An Accretion Model for the Growth of the Central BH Associated with Ionization Instability in Quasars:

Lu, Cheng, Zhang, ApJ, 2003

• AGNs produce strong radiation because the BH accretes material from the host galaxy:– A BH may acquire significant mass through accretion

• The accretion disk may not deliver all its material to the BH, as inferred from outflows in the forms of jets and galactic winds:– The ejected material may form the bulge

• So we proposed an accretion model for the coeval growth of BH and bulge.

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Model Assumptions

• Assume an initial seed BH and disk are present.• Assume accretion rate of the disk in the higher branch

of the S-shape is near Eddington-limit, and is thus modeled by the optically thick and geometrically thin solution.

• Assume a sufficient cold gas is supplied by the quasar host galaxy.

• Assume the disk in the lower branch of S-shape is modeled by relativistic advection dominated inflow-outflow solution (ADIOS).

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Basic equations

)3.....(....................0

)2.........(..........6

)1......(..........1

2

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2/12/1

2/12/1

2/12/1

unstableM

rr

rrM

r

Mrr

rr

r

M

rr

rr

rrt

out

)6........(..............................03.0~

)5.......(........................................)(1.0~

)4.......()2(

6

2

6

2

1

2

2/1

3

2/1

visoutaccbh

accbh

r

r

r

rout

bh

tmM

cml

drr

rrdr

r

rr

m

l out

in

out

in

Lower branch: ADIOS model (Becker et al.2001)

Higher branch: Keplerian model (Pringle 1981; Smak 1984)

0.025<<0.1

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outaccbhout MMM 34 103105.7

The accreted matter (Mbh)acc is about 10-3 of the total outflowing mass Mout.

3

bulge

bh4 103105.7 M

M

Based on model parameters for the accretion rates in different branches: a seed BH with mass 2106 M⊙, can grow up to BH with mass 2108 M⊙ within 10 Gyr.

Radiation efficiency in the lower branch:0.025<<0.1

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The massive seed BH problem in the early Universe• One common

problem for any kind of BH growth model: how was the massive seed BH (> 106 M⊙) produced in the early Universe?

• Some extremely massive BHs (>109 M⊙) are found at very high redshift.

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SMBH formation in the early Universe: Shen, Hu, Lou & Zhang, submitted to ApJ

• First generation stars ~100 M ⊙ (made of primordial material, almost entirely H and He) formed at z~30, but evolved quickly into supernova and left 10-100 M ⊙BHs

• A two-phase accretion model of SMBH formation:– a rapid accretion mainly of self-interacting dark

matter (SIDM) onto 10-100 M ⊙BHs to form MBH ~106 M ⊙ at very high redshift (z ~ 15 - 20)

– a subsequent growth via normal baryonic accretion at the Eddington limit to MBH ~ 109 M⊙ before redshift z ~ 6.

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Self-Interacting Dark Matter (SIDM) Accretion

• Simulations of structure formation in the Universe prefer SIDM model (angular momentum) with specific cross section: ~

• The first large-scale structures formed are dark matter halo. Assuming isothermal density profile

• Then the BH mass growth:

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Baryonic Eddington Accretion Phase

• Exponential growth of BH mass via baryonic Eddington accretion: Salpeter (1964)

• To make 109 M⊙ from 106 M⊙, it takes 5×108 years, i.e., just a few percent of the age of the Universe– However such SMBHs in the early Universe are very rare

→ most quasars are not accreting at Eddington rate continuously←our S-curve instability BH growth model- Persistent BH binaries are also very rare; most BH

binaries are transients (the same S-curve). Coincident?

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Summary• Unification model of Active Galactic Nuclei

– BH + Accretion Disk + Dusty Torus; Disk and Torus are coplanar– Most EM-radiation from disk and the torus covers part of the disk– Observed disk flux is inclination angle dependent: Type I AGNs are

normally brighter than Type II AGNs• Two models coeval growth of supermassive BH with bulge

– Mergers of smaller systems– Accretion of material from the disk (BH growth) and outflows from

the disk (bulge growth)• Formation of seed supermassive BHs

– Bondi (spherical) accretion of self-interacting dark matter halo • Growth of some supermassive BHs (in a small percentage of quasars)

in the early Universe – Eddington accretion of baryonic matter onto seed supermassive BHs.

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Further work and open questions

• Is X-ray emission from AGNs really from accretion disk?– Previously the X-ray emission is usually believed from optically

thin corona.– If the X-ray emission is really from the disk, then relativistic

effects on its continuum spectra should be revealed.- Maybe for individual AGN we can find a way to estimate its

inclination angle accurately and then study the spectral correlation with the inclination angle?

• For our two phase BH growth model, one important question to ask is: can this model reproduce the observed luminosity function of AGNs?– Which kind of accretion history is required to produce the LF?

• How much dark matter is turned into 106 M⊙ in the early Universe? Is there any way to detect these BHs?