Isotropic Mid-Infrared Emission from Active Galactic Nuclei Nancy - - PowerPoint PPT Presentation

Isotropic Mid-Infrared Emission from Active Galactic Nuclei

Nancy A. Levenson (University of Kentucky)

Chris Packham (University of Florida) James Radomski (Gemini Observatory) Rachel Mason (Gemini Observatory) Justin Schaefer (University of Florida) Charles Telesco (University of Florida)

AGN unification

Type 1 Type 2

*

Optically and geometrically thick dusty torus reprocesses intrinsic AGN continuum to emerge in the infrared Infrared luminosity depends on intrinsic AGN luminosity

AGN unification -- smooth torus

Type 1 Type 2

*

• Anisotropic MIR emission
• Type 1 strong silicate emission; Type 2 deep silicate absorption

Consequences for homogeneous torus:

AGN unification -- smooth torus models

(Pier & Krolik 1992)

Small torus

• Small scale measurements are essential!

torus size < 5pc star formation can contribute significantly on large scales

• diffraction-limited observations with Gemini

R8μm ~ 0.3” (50pc at 30Mpc)

(Díaz-Santos et al. 2008)

T

• ReCS

Small torus

• Small scale measurements are essential!

torus size < 5pc star formation can contribute significantly on large scales

• diffraction-limited observations with Gemini

R8μm ~ 0.3” (50pc at 30Mpc)

(Díaz-Santos et al. 2008)

Spitzer

Small torus

• Small scale measurements are essential!

torus size < 5pc star formation can contribute significantly on large scales

• diffraction-limited observations with Gemini

R8μm ~ 0.3” (50pc at 30Mpc)

(Díaz-Santos et al. 2008)

Mid-infrared/X-ray correlations

39 40 41 42 43 44 45 log LMIR [erg s−1] (psf fitting) 39 40 41 42 43 44 45 log LX [erg s−1] Seyfert 1 Seyfert 2

intrinsic AGN luminosity reprocessed emission

• distance-limited sample

D < 50 Mpc

• normal Seyfert galaxies
• fit PSF to MIR (to isolate

unresolved AGN)

• absorption-corrected LX

is a proxy for LAGN

• X-ray variability

type 1 uncertainty

(Levenson et al., in preparation)

Mid-infrared/X-ray correlations

39 40 41 42 43 44 45 log LMIR [erg s−1] (psf fitting) 39 40 41 42 43 44 45 log LX [erg s−1] Seyfert 1 Seyfert 2

intrinsic AGN luminosity reprocessed emission

• MIR and X-ray are

strongly correlated

• no significant differences

between types 1 and 2 isotropic MIR emission

• in agreement with

previous work

e.g., Horst+ 2008, Gandhi+ 2009

(Levenson et al., in preparation)

Mid-infrared/X-ray correlations

• type 1 and type 2 are not significantly different

isotropy of MIR emission

Type 1 Type 2

*

Inhomogeneous (clumpy) torus

σ i Rd Ro

*

N(R, β) = N0 exp(−β2/σ2)(R/Rd)−q

• Nearly isotropic MIR emission with weak silicate features

(Nenkova et al. 2008)

Inhomogeneous (clumpy) torus

*

• individual clouds are optically thick (τV ≥ 20)
• AGN directly heats some clouds
• radiative transfer within dusty clouds
• illuminated and dark sides may observed from both type 1 and 2

Inhomogeneous (clumpy) torus

• clumpy torus models produce nearly isotropic MIR emission
• isotropy increases toward longer wavelengths
• isotropy increases with a more compact torus

5 10 15 20 25 Wavelength (µm) 0.1 1.0 10.0 Relative Flux Density

i = 0o i = 90o N0=4, σ=30o, q=1, τV=40

(Levenson et al., in preparation)

Inhomogeneous (clumpy) torus

• for a given model, MIR flux typically varies by less than 5x
• considering all parameter combinations,

absolute MIR luminosity varies by less than 600x

5 10 15 20 25 Wavelength (µm) 0.1 1.0 10.0 Relative Flux Density

i = 0o i = 90o N0=4, σ=30o, q=2, τV=60

(Levenson et al., in preparation)

Inhomogeneous (clumpy) torus

8.8 μm flux as a function of viewing angle:

20 40 60 80 Viewing angle (degrees) 5 10 15 F8.8(i)/F8.8(90

• )

σ=45o, q=1

N0 2 6 10 15 τV 20 40 60 80 100

(Levenson et al., in preparation)

Mid-infrared/X-ray correlations

(Levenson et al., in preparation)

39 40 41 42 43 44 45 log LMIR [erg s−1] (psf fitting) 39 40 41 42 43 44 45 log LX [erg s−1] Seyfert 1 Seyfert 2 39 40 41 42 43 44 45 log LMIR [erg s−1] (psf fitting) 39 40 41 42 43 44 45 log LX [erg s−1] Seyfert 1 Seyfert 2 fit model

• general agreement with

theoretical predictions

• luminosity dependence here

reduced LX with stronger MIR

• sources in addition to AGN

contribute to MIR nuclear star formation, in variable amounts

Mid-infrared/X-ray correlations

(Levenson et al., in preparation)

39 40 41 42 43 44 45 log LMIR [erg s−1] (psf fitting) 39 40 41 42 43 44 45 log LX [erg s−1] Seyfert 1 Seyfert 2 fit model 39 40 41 42 43 44 45 log LMIR [erg s−1] (fixed physical aperture) 39 40 41 42 43 44 45

X

• fixed 100 pc aperture:

no luminosity dependence

• comparable star formation on these scales

Conclusions

• MIR and intrinsic (X-ray) luminosity are strongly correlated
• MIR emission is effectively isotropic
• account for these results with a clumpy AGN torus
• more isotropic with longer wavelength
• more isotropic with smaller torus
• weak silicate features in emission and absorption
• some luminosity dependence on MIR/X-ray correlation
• understand as contamination by nuclear star-heated dust
• not apparent on 100 pc scales