AGN Unification Viewed in the mid-IR

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AGN Unification Viewed in the mid-IR
Spectra

• Lei Hao
• Cornell University

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Why Mid-IR

• Dust in ISM
• oxygen-rich silicates
• carbon-rich grains

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Why Mid-IR

• Low resolution modules (SL,LL)
• 5-40?m wavelength coverage
• Resolution 64-128
• High resolution modules (SH, LH)
• 9-38?m wavelength coverage
• Resolution 600

• Dust in ISM
• oxygen-rich silicates
• carbon-rich grains

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Mid-IR spectra examples
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AGN mid-IR spectra
quasars
ULIRGs
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AGN mid-IR spectra
Seyfert1
Seyfert2
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A sample of local AGNs and ULIRGs

• Spitzer archival available, complete
• low-res spectra, zlt0.5
• Optical classification adopted from Veron-Cetty
  Veron (2006)
• 24 quasars (3 ULIRGs), 45 Seyfert 1s (7 ULIRGs),
  47 Seyfert 2s (7 ULIRGs) and 98 ULIRGs.

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Mid-IR average spectra
Hao et al. 2007, ApJ, 655, L77
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Mid-IR average spectra
(Brandl et al., 2006)
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• Deep silicate absorption in ULIRGs

Hao et al. 2007, ApJ, 655, L77
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• Silicate features in Seyferts are week

Deo et al. 2007, /0709.3076/
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• Many Seyfert 1s show absorptions
• Clumpy unification
• Host galaxy contamination
• The probability of Seyfert 1s showing SA is
  larger than the probabilities of Seyfert 2s
  showing SE.

Hao et al. 2007, ApJ, 655, L77
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• Silicate features in Quasars are mainly in
  emission

Hao et al. 2007, ApJ, 655, L77
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Maiolino et al. 2007, AA, 468 979
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Silicate features in AGN

• We finally detected the emission feature in QSOs.
• Caution does the emission come from the torus or
  host galaxies?
• Emission vs. absorption for Type I and Type II
  are clearer for high-luminosity AGN.
• Seyferts have weak silicate features, many
  Seyfert 1s have silicate absorptions.

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Mid-IR spectra examples
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• PAH strength trace the Starformation in the hosts

Weedman, et al. 2005
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• Unification Type I and Type II AGN should have
  comparable PAH strength.

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Mid-IR average spectra
(Brandl et al., 2006)
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Mid-IR average spectra

• PAH emissions are stronger in Seyfert 2s than in
  Seyfert 1s
• Similar in Buchanan et al. (2006) and Deo et al.
  (2007)
• Need a control sample

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PAH stronger in Seyfert 2s?

• Over 60 optically selected Seyfert 1s and Seyfert
  2s sampled over their OIII luminosities.

Seyfert 2s Seyfert 1s
Hao et al., in preparation
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Mid-IR spectra examples
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• Since IR is less sensitive to extinction, Then,
  Unification Type I and Type II AGN have
  comparable IR emission line properties?

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Mid-IR atomic emission lines

• Deo et al. (2007) Seyfert 1s have stronger
  OIV25.89/NeII12.81, NeIII15.56/NeII12.81,
  and NeV14.32/NeII12.81 than Seyfert 2s.
• Enhanced NeII emission in Seyfert 2s?
• Dudik et al. (2007) Seyfert 2s have lower
  NeV14.3/NeV24.3 ratios than Seyfert 1s
  extinction to NeV emitting region?

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Conclusion

• Mid-IR spectrum is a power tool in testing and
  constraining the unified view of AGN silicate
  features, PAH emissions, atomic lines, continuum
• In general, the observations support type II AGN
  have more obscuration.
• But the dust structure in AGN is more complicated.

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Conclusion

• Mid-IR spectrum is a power tool in testing and
  constraining the unified view of AGN silicate
  features, PAH emissions, atomic lines, continuum
• In general, the observations support type II AGN
  have more obscuration.
• But the dust structure in AGN is more complicated.

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Conclusion

• Mid-IR spectrum is a power tool in testing and
  constraining the unified view of AGN silicate
  features, PAH emissions, atomic lines, continuum
• In general, the observations support type II AGN
  have more obscuration.
• But the dust structure in AGN is more complicated.