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AGN: The Unified Model. Tom Esposito Astr 278 2012 Feb 09. Many different types of AGN have been observed. Seyfert 1, Seyfert 2, QSO, QSO2, LINER, FR I, FR II, Quasars, Blazars , NLXG, BALQ…. How can we explain this variety?.

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agn the unified model

AGN: The Unified Model

Tom Esposito

Astr 278

2012 Feb 09

many different types of agn have been observed
Many different types of AGN have been observed

Seyfert1, Seyfert 2, QSO, QSO2, LINER, FR I, FR II, Quasars, Blazars, NLXG, BALQ…

how can we explain this variety
How can we explain this variety?
  • All AGN are intrinsically the same and we are just viewing them differently

OR

  • Each type of AGN is a distinct phenomenon

OR

  • Some combination of 1 and 2

Unified Model

unified model consists of 2 schemes radio quiet radio loud
“Unified” Model consists of 2 schemes – radio-quiet & radio-loud

Unified Model

Radio-quiet

  • Seyfert 1
  • Seyfert 2
  • QSO
  • QSO2
  • LINERs?

Radio-loud

  • FR I, FR II
  • Quasars
  • Blazars
all radio quiet agn have the same central engine
All radio-quiet AGN have the same central engine

Supermassive black hole + hot accretion disk at center

SMBH

Accretion

Disk

Credit: C. M. Urry and P. Padovani

blr gas excited by uv photons emits broad optical lines
BLR gas excited by UV photons emits broad optical lines

Supermassive black hole + hot accretion disk at center

Hot, high velocity, dense gas clouds near BH form broad-line region

dust gas torus may obscure central regions of agn
Dust & gas torus may obscure central regions of AGN

Supermassive black hole + hot accretion disk at center

Hot, high velocity, dense gas clouds near BH form broad-line region

Compton-thick dusty torus surrounds engine and broad-line region

hot electrons outside torus and blr scatter nuclear emission
Hot electrons outside torus and BLR scatter nuclear emission

Supermassive black hole + hot accretion disk at center

Hot, high velocity, dense gas clouds near BH form broad-line region

Compton-thick dusty torus surrounds engine and broad-line region

Hot electrons scatter polarized continuum + broad-line emission

narrow emission lines from gas within ionization cones
Narrowemission lines from gas within ionization cones

Supermassive black hole + hot accretion disk at center

Hot, high velocity, dense gas clouds near BH form broad-line region

Compton-thick dusty torus surrounds engine and broad-line region

Hot electrons scatter polarized continuum + broad-line emission

Cool, low velocity, low density gas clouds beyond torus edge form narrow-line region

all agn are intrinsically type 1
All AGN are intrinsically Type 1
  • Featureless optical/UV continuum, soft and hard x-rays from nucleus
  • Broad permitted optical emission lines
  • Narrow permitted and forbidden emission lines
  • IR emission from dust reprocessing of nuclear light
spectropolarimetry suggests that type 2 agn are obscured type 1 s
Spectropolarimetry suggests that Type 2 AGN are obscured Type 1’s
  • NGC 1068 shows Type 2 spectrum overall but Type 1 spectrum in polarized light (Antonucci & Miller 1985)
    • Electrons polarize and scatter nuclear emission and broad emission lines into observer’s line-of-sight.

O

2 10 kev x ray flux is reduced in type 2 agn by torus absorption
2-10 keV x-ray flux is reduced in Type 2 AGN by torus absorption
  • Molecular gas in torus with 1024 cm-2 < NH < 1025cm-2 absorbs only low energy x-rays
  • Short-period variability of x-ray absorption implies torus inner edge < 1 pc from nucleus and no more than 10 pc in radial extent (Risaliti et al. 1999, 2002, 2005)
  • Fe K-α line reflection requires a mirror
other observational evidence is less substantial
Other observational evidence is less substantial
  • Lack of QSO2’s matches prediction of large torus opening angle at high luminosities
    • Requires AGN to have different-sized tori, which is a modification of the standard unified model
  • Clumpy torus models can explain mid-IR SED’s of Type 2 AGN
    • But is a clumpy torus still the Unified Model???
evidence against the unified model or not
Evidence against the Unified Model or not?
  • Recent efforts to reproduce mid-IR observations of Type-1 and Type-2 Seyferts by Almeida et al. 2011 used clumpy torus models
  • They found more dependence on torus morphology than inclination
    • Type-2’s have broader, clumpier, more opaque tori
  • Does this matter much to the Unified Model?
summary
Summary
  • Unified Model asserts that differences between Type 1 and Type 2 AGN are due to viewing angle only!
  • Optical/UV, IR, and x-ray observations support this model to a degree
  • Radio-loud AGN are unified with similar scheme to radio-quiet but with less certainty
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