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

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)



N h l l edd plane
NH-L/LEdd plane

Raimundo, Fabian, Bauer et al. 2010



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 Model?

  • 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 Model?

  • 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 Model?

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

Radio quiet

Radio loud


Lightcurve amplitudes
Lightcurve amplitudes Model?

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 Model?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 Model?

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 Model?

Black body from hot dust

Diamond-Stanic et al. 2009

Evidence of hot dust in WLQ


Conclusions
Conclusions Model?

  • 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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