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AGN Unification AGN Unification Viewed in the mid-IR Viewed in the mid-IR
Lei HaoLei HaoCornell UniversityCornell University
Spectra
22
Why Mid-IRWhy Mid-IR
Seyfert2s, Type II
Seyfert1s, Quasars, Type I
Narrow emission lines
Broad emission lines
Silicate dust absorption
Silicate dust emission
Dust in ISM:
•oxygen-rich silicates
•carbon-rich grains
33
Why Mid-IRWhy Mid-IR
Seyfert2s, Type II
Seyfert1s, Quasars, Type I
Narrow emission lines
Broad emission lines
Silicate dust absorption
Silicate dust emission
Dust in ISM:
•oxygen-rich silicates
•carbon-rich grains
Low resolution modules (SL,LL)Low resolution modules (SL,LL) 5-405-40m wavelength coveragem wavelength coverage Resolution: 64-128Resolution: 64-128
High resolution modules (SH, High resolution modules (SH, LH)LH) 9-389-38m wavelength coveragem wavelength coverage Resolution: 600Resolution: 600
44
Mid-IR spectra examples
QSO
ULIRG
Seyfert
Starburst
Silicate features
Si-O stretchin
g
O-Si-O bending
77
Spitzer archival available, complete Spitzer archival available, complete
low-res spectra, z<0.5low-res spectra, z<0.5Optical classification adopted from Optical classification adopted from
Veron-Cetty & Veron (2006) Veron-Cetty & Veron (2006) 24 quasars (3 ULIRGs), 45 Seyfert 1s 24 quasars (3 ULIRGs), 45 Seyfert 1s
(7 ULIRGs), 47 Seyfert 2s (7 ULIRGs) (7 ULIRGs), 47 Seyfert 2s (7 ULIRGs) and 98 ULIRGs.and 98 ULIRGs.
A sample of local AGNs and A sample of local AGNs and ULIRGsULIRGs
1010
• Deep silicate absorption
in ULIRGs
SE SA
)10(
)10(ln10 mf
mfS
cont
obs
Hao et al. 2007, ApJ, 655, L77
1111
Silicate features in Seyferts are Silicate features in Seyferts are weekweek
Deo et al. 2007, /0709.3076/
1212
• 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.
SE SA
)10(
)10(ln10 mf
mfS
cont
obs
Hao et al. 2007, ApJ, 655, L77
1313
SE SA
Hao et al. 2007, ApJ, 655, L77
Silicate features Silicate features in Quasars are in Quasars are mainly in mainly in emissionemission
1515
Silicate features in AGNSilicate features in AGN
We finally detected the emission We finally detected the emission feature in QSOs.feature in QSOs.Caution: does the emission come from the Caution: does the emission come from the
torus or host galaxies?torus or host galaxies?Emission vs. absorption for Type I and Emission vs. absorption for Type I and
Type II are clearer for high-luminosity Type II are clearer for high-luminosity AGN.AGN.
Seyferts have weak silicate features, Seyferts have weak silicate features, many Seyfert 1s have silicate many Seyfert 1s have silicate absorptions.absorptions.
Hao et al. 2005c, ApJ, 625, L75
See also Siebenmorgen et al. 2005, Sturm et al., 2005
1616
PAH (Polycyclic Aromatic Hydrocarbon)emissions (C-H and C-C stretching and bending
modes)
Mid-IR spectra examples
QSO
ULIRG
Seyfert
Starburst
1717
Weedman, et al. 2005
PAH strength trace the PAH strength trace the Starformation in the hostsStarformation in the hosts
1818
Unification: Type I and Type II AGN Unification: Type I and Type II AGN should have comparable PAH should have comparable PAH
strength.strength.
2020
Mid-IR average spectraMid-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
2121
PAH stronger in Seyfert 2s?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
2323
SinceSince IR is less sensitive to IR is less sensitive to extinction, extinction, ThenThen, Unification: Type I , Unification: Type I and Type II AGN have comparable and Type II AGN have comparable
IR emission line properties?IR emission line properties?
2424Deo et al. 2007
Mid-IR atomic emission linesMid-IR atomic emission linesDeo et al. (2007): Seyfert 1s have
stronger [OIV]25.89/[NeII]12.81, [NeIII]15.56/[NeII]12.81, and [NeV]14.32/[NeII]12.81 than Seyfert 2s.
Enhanced [NeII] emission in Seyfert 2s?Dudik et al. (2007): Seyfert 2s have
lower [NeV]14.3/[NeV]24.3 ratios than Seyfert 1s: extinction to [NeV] emitting region?
Dudik et al. 2007
2525
Conclusion Conclusion Mid-IR spectrum is a power tool in Mid-IR spectrum is a power tool in
testing and constraining the unified view testing and constraining the unified view of AGN: silicate features, PAH emissions, of AGN: silicate features, PAH emissions, atomic lines, continuum…atomic lines, continuum…
In general, the observations support type In general, the observations support type II AGN have more obscuration.II AGN have more obscuration.
But the dust structure in AGN is more But the dust structure in AGN is more complicated.complicated.
2626
Conclusion Conclusion Mid-IR spectrum is a power tool in Mid-IR spectrum is a power tool in
testing and constraining the unified view testing and constraining the unified view of AGN: silicate features, PAH emissions, of AGN: silicate features, PAH emissions, atomic lines, continuum…atomic lines, continuum…
In general, the observations support type In general, the observations support type II AGN have more obscuration.II AGN have more obscuration.
But the dust structure in AGN is more But the dust structure in AGN is more complicated.complicated.
2727
Conclusion Conclusion Mid-IR spectrum is a power tool in Mid-IR spectrum is a power tool in
testing and constraining the unified view testing and constraining the unified view of AGN: silicate features, PAH emissions, of AGN: silicate features, PAH emissions, atomic lines, continuum…atomic lines, continuum…
In general, the observations support type In general, the observations support type II AGN have more obscuration.II AGN have more obscuration.
But the dust structure in AGN is more But the dust structure in AGN is more complicated.complicated.