Dusty torus formation by anisotropic radiative feedback of active galactic nuclei
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Dusty Torus Formation by Anisotropic Radiative Feedback of Active Galactic Nuclei. Shuang-Nan Zhang , Yuan Liu , Jin Zhang Institute of High Energy Physics and National Astronomical Observatories of China Chinese Academy of Sciences. Liu,Y. & Zhang, S.N., 2011, ApJL, 728, L44.

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Dusty Torus Formation by Anisotropic Radiative Feedback of Active Galactic Nuclei

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Dusty torus formation by anisotropic radiative feedback of active galactic nuclei

Dusty Torus Formation by Anisotropic Radiative Feedback of Active Galactic Nuclei

Shuang-Nan Zhang, Yuan Liu, Jin Zhang

Institute of High Energy Physics

and

National Astronomical Observatories of China

Chinese Academy of Sciences

Liu,Y. & Zhang, S.N., 2011, ApJL, 728, L44


The unified model of agn

The unified model of AGN

Formation?

Dusty torus

Evolution?


Agn feedback

AGN feedback

The normal of the accretion disk

  • The distribution of the dust is anisotropic

  • The UV/optical radiation from the accretion disk is also anisotropic

  • The effect of radiation pressure is significant due to the presence of dust

Observer & dust

A~500


The evolution of agns

The evolution of AGNs

A

B

C

Momentum effect of radiation


Evaporation radius

Evaporation radius

The inner radius of dust

Energy effect of radiation


Torus formation time scale 10 5 6 yr for 10 pc

Torus formation time scale: ~105-6 yr for 10 pc

~0.2 ly

Radiation pressure

1 year

Evaporation

L=1044 erg/s; L/LEdd=0.1; a=0.1 mm; A=100

a:dust radius

Hot low density gas:

Seed for BLR?

Empty

Vertical distance from the disk Z (pc)


The profile of a dusty torus

The profile of a dusty torus


N h l l edd plane

NH-L/LEdd plane

Raimundo, Fabian, Bauer et al. 2010


The fraction of type 2 agns

The fraction of type 2 AGNs

Hasinger 2008


The inner radius of dusty torus

The inner radius of dusty torus

Suganuma et al. 2006


The evolution of dusty torus

The evolution of dusty torus

Luminous, with torus, but without bright BLR

105-6 yr

?

Low

density

gas

High density clouds


Weak line quasars

Weak line quasars

Shemmer et al. 2009; EW<5 A; continuum similar to normal quasars


Radio quiet bl lac

Radio quiet BL Lac

No obvious emission lines

Plotkin et al. 2009


Are wlqs and radio quiet bl lac the objects predicted by our model

Are WLQs and Radio Quiet BL Lac the Objects Predicted by Our Model?

  • Predictions

    • Luminous accretion disk emission

    • Existence of Dusty Torus

  • Tests

    • Low polarization  disk not jet

    • Low variability  disk not jet

    • Hot dust emission  torus illuminated by luminous disk


Polarization test radio quiet bl lac

Polarization Test: radio quiet BL Lac

  • Very low polarization in continuum spectra: only two of 25 candidates are observed with weak polarization (Heidt & Nilsson 2011); non detection for all others

  • The continuum spectrum is consistent with disk origin


Long term variability test

Long Term Variability Test

  • So far observations are quite limited

  • Weaker than radio loud BL Lac?

  • Need more observations

Plotkin et al. 2010


Long term variability test1

Long Term Variability Test

  • SDSS Stripe 82(12 radio quiet BL Lac,4 WLQ,27 radio loud BL Lac)

Radio quiet

Radio loud


Lightcurve amplitudes

Lightcurve amplitudes

Radio loud

Radio quiet


Four sdss radio quiet bl lac observed with lijiang 2 4 m at v i and r bands

Four SDSS Radio Quiet BL Lac Observed with Lijiang 2.4 m at V, I and R bands

SDSS 094533.99+100950.1

SDSS 094533.99+100950.1

081250.80+522530.8

085025.60+342750.9

085025.60+342750.9

090107.64+384658.8


Very weak short timescale variability

Short Term Variability Test

Very weak short timescale variability!

m(BL Lac)-m(Star)

Time (Hour)


Hot dust test in weak line quasars

Hot Dust Test in weak line quasars

Black body from hot dust

Diamond-Stanic et al. 2009

Evidence of hot dust in WLQ


Conclusions

Conclusions

  • The distribution of dusty gas should also be anisotropic due to the influence of the anisotropic disk radiation.

  • Ourmodel can explain the presence of some obscured AGNs with high Eddington ratios and can also reproduce the observed decreasing fractionof type 2 AGNs with increasing luminosity.

  • Our model predicts the existence of luminous AGNswith dusty tori, but without luminous broad line regions.

    • Weak line quasars and radio quiet BL Lac?

      • Weak polarization, low variability and hot dust feature confirm our model predictions.

Liu,Y. & Zhang, S.N., 2011, ApJL, 728, L44


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