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
1
The unified model of AGN
Formation？
Dusty torus
Evolution？
2/21
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
3/21
The evolution of AGNs
A
B
C
Momentum effect of radiation
4/21
Evaporation radius
The inner radius
of dust
Energy effect of radiation
5/21
The profile of a dusty torus
6/21
NH-L/LEdd plane
Raimundo, Fabian, Bauer et al. 2010
7/21
The fraction of type 2 AGNs

M L
Hasinger 2008
8/21
The inner radius of dusty torus
2.6
2.4
log (days)
2.2
2
1.8
1.6
1.4
1.2
Suganuma et al. 2006
1
-23
-22
-21
-20
-19
M
-18
-17
-16
V
9/21
The evolution of dusty torus
Luminous, with torus,
but without bright BLR
10/21
Weak line quasars
Shemmer et al. 2009; EW<5 A;
continuum similar to normal quasars
11/21
Radio quiet BL Lac
No obvious
emission lines
Plotkin et al. 2009
12/21
Are WLQs and Radio Quiet BL Lac the
Objects Predicted by Our Model?
 Predictions
 Luminous
accretion disk emission
 Existence of Dusty Torus
 Tests
polarization  disk not jet
 Low variability  disk not jet
 Hot dust emission  torus illuminated by luminous
disk
 Low
13/21
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
14/21
Long Term Variability Test
 So
far
observations
are quite
limited
 Weaker than
radio loud BL
Lac？
 Need more
observations
Plotkin et al. 2010
15/21
Long Term Variability Test

SDSS Stripe 82（12 radio quiet BL Lac，4 WLQ，
27 radio loud BL Lac）
025612.47-001057.8
003808.50+001336.5
18.6
19.6
19.7
Radio quiet
18.8
Radio loud
19.8
r
19.9
19
20
r 19.2
20.1
20.2
19.4
20.3
19.6
20.4
20.5
5.1
5.15
5.2
5.25
5.3
MJD
5.35
5.4
5.45 19.8
5.1
4
x 10
5.15
5.2
5.25
5.3
MJD
5.35
5.4
5.45
4
x 10
16/21
Lightcurve amplitudes
4
10
Radio loud
3
2/DOF
10
2
10
1
10
Radio quiet
0
10
17
17.5
18
18.5
19
19.5
20
20.5
r (SDSS)
17/21
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
085025.60+342750.9
085025.60+342750.9
081250.80+522530.8
090107.64+384658.8
18/21
Short Term Variability Test
m(BL Lac)-m(Star)
 2 / DOF=7.3/15
 2 / DOF=20.1/26
 2 / DOF=38.3/25
 / DOF=24.8/19
2
Time (Hour)
Very weak short timescale variability!
19/21
Hot Dust Test in weak line quasars
Black body
from hot dust
Diamond-Stanic et al. 2009
Evidence of hot dust in WLQ
20/21
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
21/21