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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 Physicsand
National Astronomical Observatories of ChinaChinese Academy of Sciences
Liu,Y. & Zhang, S.N., 2011, ApJL, 728, L44
2/21
The unified model of AGN
Dusty torus
Formation？
Evolution？
3/21
AGN feedback 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
The normal of the accretion disk
observer
A~500
4/21
The evolution of AGNs
A B C
Momentum effect of radiation
5/21
Evaporation radiusThe inner radius of dust
Energy effect of radiation
6/21
The profile of a dusty torus
7/21
NH-L/LEdd plane
Raimundo, Fabian, Bauer et al. 2010
8/21
The fraction of type 2 AGNs
Hasinger 2008
M L
9/21
The inner radius of dusty torus
-23 -22 -21 -20 -19 -18 -17 -161
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
MV
log
(d
ays
)
Suganuma et al. 2006
10/21
The evolution of dusty torusLuminous, with torus, but without bright BLR
11/21
Weak line quasars
Shemmer et al. 2009; EW<5 A; continuum similar to normal quasars
12/21
Radio quiet BL Lac
Plotkin et al. 2009
No obvious emission lines
13/21
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
14/21
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
Polarization Test: radio quiet BL Lac
15/21
Long Term Variability Test So far
observations are quite limited
Weaker than radio loud BL Lac？
Need more observations
Plotkin et al. 2010
16/21
Long Term Variability Test SDSS Stripe 82（ 12 radio quiet BL Lac， 4
WLQ， 27 radio loud BL Lac）
5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45
x 104
19.6
19.7
19.8
19.9
20
20.1
20.2
20.3
20.4
20.5
025612.47-001057.8
r
MJD5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45
x 104
18.6
18.8
19
19.2
19.4
19.6
19.8
003808.50+001336.5
MJD
r
Radio quiet Radio loud
17/21
Lightcurve amplitudes
17 17.5 18 18.5 19 19.5 20 20.510
0
101
102
103
104
r (SDSS)
2/DOF
Radio loud
Radio quiet
18/21
Four SDSS Radio Quiet BL Lac Observed with Lijiang 2.4 m at V, I and R bands
SDSS 094533.99+100950.1 081250.80+522530.8
085025.60+342750.9 090107.64+384658.8
SDSS 094533.99+100950.1
085025.60+342750.9
19/21
Very weak short timescale variability! Time (Hour)
m(B
L La
c)-m
(Sta
r)
2 / DOF=7.3/15 2 / DOF=20.1/26
2 / DOF=24.8/192 / DOF=38.3/25
Short Term Variability Test
20/21
Hot Dust Test in weak line quasars
Black body from hot dust
Diamond-Stanic et al. 2009
Evidence of hot dust in WLQ
21/21
Conclusions The distribution of dusty gas should also be anisotropic due
to the influence of the anisotropic disk radiation. Our model can explain the presence of some obscured
AGNs with high Eddington ratios and can also reproduce the observed decreasing fraction of type 2 AGNs with increasing luminosity.
Our model predicts the existence of luminous AGNs with 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
