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

55

AGN mid-IR spectraAGN mid-IR spectra

ULIRGs quasars

66

Seyfert1

Seyfert2

AGN mid-IR spectraAGN mid-IR spectra

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

88

Mid-IR average spectraMid-IR average spectra

Hao et al. 2007, ApJ, 655, L77

99

Mid-IR average spectraMid-IR average spectra

(Brandl et al., 2006)

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

1414Maiolino et al. 2007, A&A, 468 979

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.

1919

Mid-IR average spectraMid-IR average spectra

(Brandl et al., 2006)

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

2222

Mid-IR spectra examples

QSO

ULIRG

Seyfert

Starburst

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

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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.