The nature and structure of obscuration Roberto Maiolino Astronomical Observatory of Rome Guido Risaliti Arcetri Astrophysical Observatory
The nature and structureof obscuration
Roberto MaiolinoAstronomical Observatory of Rome
Guido RisalitiArcetri Astrophysical Observatory
400 pc
2”=140pc
CO
[OIII]
Schinnerer+00Tacconi+
Obscuration on large scales (>100 pc)~
Malkan+97
Guainazzi+05 dust
Comptonthin Compton
thick
dust lanesmolecular rings/diskshost galaxy obsuration
Compton thinAV ~ a few mags
Obscuration on small scales («100pc)
IRAM - 12CO(2-1)
2” = 140pc
Schinnerer+00
NGC1068
10pc
Davies+07
SINFONI - H2 (1-0)S1
1 pc3 pc
VLTI - MIR
VLBA - H2O maserVLBA - Continuum
Jaffe+04
Greenhill+97Gallimore+97
X-ray absorption on small scales: NH variability
toru
s
BLR
Risaliti+ 02
Δt ~ years
X-ray absorption on small scales: NH variability
toru
s
BLR
Risaliti+ 02
Δt ~ years
Risaliti+ 06Elvis+ 05Puccetti+ 06
Δt ~ weeks
X-ray absorption on small scales: NH variability
toru
s
BLR
Risaliti+ 02
Δt ~ years
Risaliti+ 06Elvis+ 05Puccetti+ 06
Δt ~ weeks
toru
s
BLR
Dust absorption on small scales:inner radius ~ sublimation radius > BLR
NIR NIROpt/UV
BroadLines
NIR (K-band)
Sy1’s near-IR reverberation Suganuma+06
Rin ∝ L0.5
0.01 - 0.3 pc
Δt
Bulk of X-rayabsorption ~ BLR < dust sublimation radius
⇓- decoupling of dust and gas obscuration- AV/NH « Galactic
Nardini+07
Especially relevant at mid-IR wavelengths:AGNs are never totally absorbed at 5-20µm (A8µm< 3mag)⇒ mid-IR excellent window to detect AGNs
A8µm~0
A8µm~0.5
A8µm~2
However X-ray and dusty absorbersgenerally know each other...
optical classification
Log NH (cm-2) NHX (cm-2)
9.7
µm
sili
cate
stre
ngth
Risaliti+99 Shi+06Hao+07
mid-IR absorption
⇒ generally ~ coplanar dustyabsorber
dustyabsorberX-ray
absorber
absorption
Geometry and structure of the dusty absorber
Uniform dust distribution models
Broad IR SED-> wide range of Tdust
Large torus (~100 pc) required...Granato+97
Geometry and structure of the dusty absorber
Uniform dust distribution models
Broad IR SED-> wide range of Tdust
Large torus (~100 pc) required...Granato+97
...but high-resolution 10-20µm data -> ~pc scale
Jaffe+04Ponchelet+06
Mason+06
T = 320 K
R ≤ 1.7 pc
Clumpy models:wide Temperature range on small scales
λ (µm)
λ F λ
Nenkova+02,06Elitzur+06Hönig+06
Rin = RsublimationRout ≈ 5-30 Rin
-200 0 200
-200
0
200
DE
C in
mas
RA in mas
Clumpy models: some warnings
VLTI - 11µmCIRCINUS nucleus
flux model distribution
size ~ 0.2 pcellipticity = 0.6T = 330 K
maserdisk
plane
ionization
coneTristram+07
N2H+(1-0)
M ~ 5 MMW molecular core
gas-dust properties ≠ diffuse ISM
Caselli+02
Dust properties in AGNs
Extinction curves give different results
QSO1’sSMC-like ⇒ small grains
Reichards+03, Hopkins+04
strongly reddened AGNsflattened ⇒ large grainsGaskell+04,06Czerni+04(Willott+05)
No contradiction:they sample differentmedia
Sani+07
Dust properties in AGNs
τcont
τ CO
,Hyd
roc.
Continuum anddusty featuresabsorptions do
not correlate
broad variety of dust properties
⇓
Stability of thedusty absorber
Must cover a large solid angle (~60-80%)⇒ geometrically thick (as observed)
- Radiation pressure Krolik’07
- Warped disk (observed in maser emission) Nayakshin’05, Caproni+06
- Not static, but dynamical stability: outflowing clouds Elitzur+06, Elvis+02,03 Everett & Konigl 00
- Nuclear stellar winds Nayakshin+06
- Turbolence by SNe Wada+04, Watabe+05 evidence for recent
nuclear starburstDavies+06, Mueller-Sanchez+06SDSS results -> Heckman’s talk
Evidence for alternative geometriesPowerful, obscured AGNs
without NLR(generally U/LIRGs)
Imanishi+07,04, Franceschini+03,Maiolino+03, Ballo+04, Caccianiga+07...
in some cases theNLR is obscured
by dust in the host galaxyHaas+06
talks by Martinez-Sansigre,Polletta, Alonso-Herrero
in some cases theNLR does not exist
Armus+07
6.2µm PAH EW (µm)
[NeV
]14.
3µm
/ [N
eII]1
2.8µ
m
4π nuclear obscuration?
Covering factor versus luminosityContrasting results from X-ray and optical surveys
Ueda+ 04, Simpson+05, La Franca+05,Hasinger’06, Barger+05, Akylas+06,Steffen+04
AGN2 / AGN1 ratiodecreases with luminosity
Dwelly+06, Wang+07
Ascribe the effect to incompleteness and selection effectssee also Zakamska’s talk
Covering factor versus luminosityAlternative approach: use only AGN1s
Maiolino+07
(but missing obscuration onhost galaxy scales)
IRbump
bluebump
νlo
g [ λ
Lλ(6
.7µ
m) /
λLλ
(510
0A) ]
Covering factor versus luminosity
Alternative approach: use only AGN1s
Bianchi+07
Same result forthe X-ray Compton thick
absorber/reflector
Iwasawa-Taniguchi effect (Balwdin for FeK line)L(2-10 keV) [1044 erg s-1]
EW
(FeK
line
) [e
V]IR
bumpblue
bump X-raycont.
FeK
ν
Physical origin of the Covering Factor (CF) dependence on luminosity
+ “Receding torus” (increasing Rsublimation) Lawrence’91 - does not match observed trends Simpson’05 - only for dusty torus
+ Gravitational effect of BH and galactic disk Lamastra+06 - CF should correlate with MBH
+ Radiation pressure - CF should correlate with L/LEdd
Covering factor inconsistencybetween local and high-z Sy’s
AGN1
AGN2 thin
Gilli+ 07
Alonso-Herrero+06, Fiore+07,Daddi+07, Martinez-Sansigre+06,
Polletta+06, Tozzi+06
Resolved X-ray background (