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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.

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Dusty Torus Formation by Anisotropic Radiative Feedback of Active Galactic Nuclei

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  1. 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

  2. The unified model of AGN Formation？ Dusty torus Evolution？

  3. 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

  4. The evolution of AGNs A B C Momentum effect of radiation

  5. Evaporation radius The inner radius of dust Energy effect of radiation

  6. 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)

  7. The profile of a dusty torus

  8. NH-L/LEdd plane Raimundo, Fabian, Bauer et al. 2010

  9. The fraction of type 2 AGNs Hasinger 2008

  10. The inner radius of dusty torus Suganuma et al. 2006

  11. The evolution of dusty torus Luminous, with torus, but without bright BLR 105-6 yr ? Low density gas High density clouds

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

  13. Radio quiet BL Lac No obvious emission lines Plotkin et al. 2009

  14. 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

  15. 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

  16. Long Term Variability Test • So far observations are quite limited • Weaker than radio loud BL Lac？ • Need more observations Plotkin et al. 2010

  17. Long Term Variability Test • SDSS Stripe 82（12 radio quiet BL Lac，4 WLQ，27 radio loud BL Lac） Radio quiet Radio loud

  18. Lightcurve amplitudes Radio loud Radio quiet

  19. 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

  20. Short Term Variability Test Very weak short timescale variability! m(BL Lac)-m(Star) Time (Hour)

  21. Hot Dust Test in weak line quasars Black body from hot dust Diamond-Stanic et al. 2009 Evidence of hot dust in WLQ

  22. 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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