Towards the Grand Unification of AGNs in Hierarchical Cosmologies

Nikos Fanidakisand

C.M. Baugh, R.G. Bower, S. Cole, C. Done, C.S. Frenk

January 30, 2009

Outline

• Supermassive black hole (SMBH) growth in hierarchical cosmologies

• Cosmological black hole (BH) spin evolution

• Predicting the radio loudness of AGNs • Conclusions

Mass, SpinMass, Spin

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i. Dimensionless spin parameter : a = cJBH /GMBH2

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ii. 0 ≤ a ≤ 0.998 :a = 0 →Schwarzschild BH

a = 0.998 → Maximally rotating BH

⎧ ⎨ ⎩

Rotating BHs in Astrophysics

Black holes are the simplest objects in the Universe.

They can be completely described by just two parameters, the mass

and the spin.

Black holes are the simplest objects in the Universe.

They can be completely described by just two parameters, the mass

and the spin.

Supermassive Black Holes in ΛCDM

• SMBHs reside at the centres of all galaxies with spheroids.

• Channels of SMBH growth: Hot gas accretion:

quiescent accretion from hot halo.

Cold gas accretion: accretion of gas during galaxy mergers and disk instabilities.

BH binary mergers.• The growth of mass

affects the evolution of the BH spin.

Supermassive Black Holes in ΛCDM

• SMBHs reside at the centres of all galaxies with spheroids.

• Channels of SMBH growth: Hot gas accretion:

quiescent accretion from hot halo.

Cold gas accretion: accretion of gas during galaxy mergers and disk instabilities.

BH binary mergers.• The growth of mass

affects the evolution of the BH spin.

BH spin change in astrophysical processes

• BH mergers

M1, S1

M2, S2

L2 Binary BHs form during galaxy

mergers. The system hardens due to the

emission of gravitational waves – the two members eventually merge.

During the merger the satellite BH transfers its angular momentum and spin to the central BH.

The final remnant is always a rotating BH.

• BH accretionlast stable orbit

accretion disk

Gas accreted via an accretion disk transfers its angular momentum at the last stable orbit to the BH:• Co-rotating gas – spin up• Counter-rotating gas – spin

down The size of the disk is limited by its

self-gravity: A single accretion event of Macc gives rise to a series of separated accretion episodes.

Spin Distributions

AGN Jets

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L jet ∝ (H /R)2 Bφ2MBH ˙ m a2

Imag

e s

ou

rce:

Nara

yan

+0

5

M87

• Jet formation:• Twisted magnetic

lines collimate outflows of plasma.

• The jet removes energy from the disk/BH.

• The plasma trapped in the lines accelerates and produces large-scale flows.

• The jet power increases proportionally to the BH spin:

Blandford & Znajek 1977

AGN radio loudness dichotomy

AGN radio loudness: Observational factsAGN radio loudness: Observational facts

• AGNs can be divided into two classes:– Radio-loud objects (jets

dominate radio emission)– Radio-quiet objects (negligible

emission from jets)• AGNs form two distinct

sequences on the Lbol –Lradio plane:– Upper sequence: objects hosted

by giant ellipticals with MSMBH>108M

– Lower sequence: objects hosted mainly by spirals with MSMBH<108M

• Spin paradigm: the BH spin is assumed to determine the radio loudness of an AGN

Radio-loud objects

Radio-quiet objects

Data: Sikora et al. 2007

AGNs in GALFORM: modelling the disk/jet

Accretion in GALFORM spans a wide range of accretion rates: Note: The geometry of the disk depends on the accretion rate!

Accretion in GALFORM spans a wide range of accretion rates: Note: The geometry of the disk depends on the accretion rate!

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˙ m Thin disk

ADAF

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10−6 ≤ ˙ m ≤102, ˙ m = ˙ M / MEdd*

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i) ˙ m ≥ 0.01: Thin Accretion Disks

Disk → Lbol,TD = εMBH ˙ m c 2

Jet → L jet,TD = 4 ×1036 MBH1.1 ˙ m 1.2a2

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ii) ˙ m ≤ 0.01: Advection Dominated

Accretion Flows (ADAFs)

Disk → Lbol,ADAF ∝ MBH ˙ m 2

Jet → L jet ,ADAF = 2 ×1038 MBH ˙ m a2

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* MEdd ∝ MBH

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H ~ R

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H << R

Meie

r 1999

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L jet ∝ (H /R)2 Bφ2MBH ˙ m a2Remem

ber:

AGN radio loudness: theoretical predictions

AGN radio loudness: theoretical predictions

Conclusions

• We have developed a model using GALFORM for explaining the radio loudness of AGNs.

• Our results seem to reproduce reasonably well with the observational data.

• In our model the spin and the accretion rate define the radio loudness of an AGN.

Future work• Radio/X-ray luminosity functions• RL/RQ AGN clustering• AGN feedback (?)

Quasar LF

Warped accretion disks