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The cosmic spin of SMBHs from radio observations

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The cosmic spin of SMBHs from radio observations

Alejo Martínez Sansigre (ICG-Portsmouth)

&

Steve Rawlings (Oxford)

Assumptions:

Bolometric Luminosity

Jet power

e.g. Mckinney (2005), Hawley & Krolik (2006), Nemmen et al. (2007), Benson & Babul (2009), Tchekhovskoy et al. (2010).

Leiden, Feb 2011

Assumptions:

Bolometric Luminosity

Accretion rate

Jet power

e.g. Mckinney (2005), Hawley & Krolik (2006), Nemmen et al. (2007), Benson & Babul (2009), Tchekhovskoy et al. (2010).

Leiden, Feb 2011

Assumptions:

Radiative efficiency

Bolometric Luminosity

Accretion rate

Jet power

Jet efficiency

e.g. Mckinney (2005), Hawley & Krolik (2006), Nemmen et al. (2007), Benson & Babul (2009), Tchekhovskoy et al. (2010).

Leiden, Feb 2011

Radio loudness of quasars?

Radio-loudness of quasars

Spin

Accretion

Data from Cirasuolo et al. (2003)

Martinez-Sansigre & Rawlings (2011)

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Can we explain the radio luminosity function?

The radio LF

P. Best private communication

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Modelling the HEGs with QSOs

Can convert Lx to accretion rate

Silverman et al. (2008)

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Modelling the LEGs with ADAFs

BH mass function

Graham et al. (2007)

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Modelling the LEGs with ADAFs

Distribution of Eddington ratios (flat prior due to ignorance)

BH mass function

Graham et al. (2007)

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Fit to the RLF

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Best-fitting distributions

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Prediction z=1 RLF

Radio LFs from Willott et al. (2001) and Smolcic et al. (2009)

Martinez-Sansigre & Rawlings (2011)

Leiden, Feb 2011

Compare to cosmological simulations

Fanidakis et al. (2010)

Martinez-Sansigre & Rawlings (2011)

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Spin history

Low-z

Low accn rate

High spin peak

High-z

High accn rate

All spin low

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Chaotic accretion + mergers

Chaotic accretion leads to low spins

Martinez-Sansigre & Rawlings (2011)

Leiden, Feb 2011

Chaotic accretion + mergers

Chaotic accretion leads to low spins

Recent major mergers lead to high spins

Martinez-Sansigre & Rawlings (2011)

Leiden, Feb 2011

Interpretation

- Physically, at z=0 the radio LF is dominated by low-accretion rate objects with high spins
- A small fraction, however, originates in high-accretion rate objects with low spin
- At higher redshifts, the density of high-accretion low-spin objects increases, an they eventually dominate the radio LF.
- This means that the mean spin is higher at low redshift, and lower at high redshift.
- This is consistent with the picture of chaotic accretion spinning SMBHs down, and major mergers spinning them up.

Leiden, Feb 2011

Thank you!

For more info: Martínez-Sansigre & Rawlings, MNRAS (2011), ArXiv: 1102.2228

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Parametric forms for spin distribution

Power-law distribution

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Parametric forms for spin distribution

Single-gaussian distribution

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Parametric forms for spin distribution

Double gaussian

distribution

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Parametric forms for spin distribution

Bayesian evidence chooses the double gaussian

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Jet efficiency

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Comparison to entire RLF

Leiden, Feb 2011

Martinez-Sansigre & Rawlings (2011)

Spin-down: chaotic accretion

Infalling gas from the galaxy is NOT expected to all be in the same angular momentum plane

Co- or counter-alignment will occur depending on relative J and orientation

Overall effect is for chaotic accretion to spin down a rapidly rotating SMBH, typically to a~0.1

King et al. (2006,2008)

Leiden, Feb 2011

Spin history

Martinez-Sansigre & Rawlings (2011)

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Spin-up mechanism: BH mergers

Major mergers of low spin BHs leads to high spin coalesced BHs.

BH merger formula from Rezzolla et al. (2008)

Leiden, Feb 2011

Spin-up mechanism: BH mergers

Assume a Poisson distribution with a mean of 0.7 major mergers (following Robaina et al. 2010)

BH merger formula from Rezzolla et al. (2008)

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ADAF component

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QSO component

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Radiative efficiency

Novikov & Thorne (1973), Mckinney & Gammie (2004), Beckwith et al. (2008,) Noble et al. (2009), Penna et al. (2010)

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Producing jets

Figure from:

J. Krolik’s webpage

Leiden, Feb 2011