Probing the Geometry and Physics of the Emission Region of Active Galactic Nuclei Using Hard X-Ray Observations

Natasha WoodsMentors: Marco Ajello & Masaaki Hayashida

Outline

• AGN & Unified Model• Testing the Unified Model• Results• Conclusions

Introduction

• AGN–Majority of energy output unrelated to stellar

processes– Compact regions, galaxy center, exceedingly

luminous• Classification– Radio luminosity– Spectral properties

Unified Model for AGN

• All AGN are intrinsically the same

• Perceived differences due to viewing orientation

• SMBH, accretion disk, molecular torus, corona

Seyfert Galaxies

Evidence For & Against the Unified Model

• Polarized broad emission lines in Sy2

• Sy1 <---> Sy2• Electron temperature • Fraction of absorbed

sources

X-ray Spectra

• X-Rays• IC Radiation• Direct, Transmitted,

Reflected

Reflection Component

• IC reflection peak ~30keV, softening spectra (whiteboard)

• Sy1 should have a larger reflection component and photon index than Sy2

High Energy Cut-off

• Corona's electrons expected to be thermal• Cut-offs for Sy1 and Sy2 should be compatible,

corona's properties are independent of orientation

Relevance

• ~100% CXB• Constrain cosmological models and black hole

physics

Sample Population

• ~200 sources• Swift-BAT hard X-ray Survey• 5 sigma significance level• 3 years exposure• Unbiased, blind search

Models for Spectra

•Simple power law model (SPL) fit to individual spectra in Xspec11

Photon Index Histograms

Gaussian and Weighted Averages• Gaussian poorly

fit some data• Weighted

Averages– based on errors– no model

Stacked Spectra

• S/N, mean properties• SPL and PEXRAV fit to spectra

Results: SPL Histograms• (KS p-values)

Results: SPL & PEXRAV Stacked Spectra

• PEXRAV>SPL• Photon

Indices• Reflection • Energy Cut-

off

Conclusion

• Photon Index Sy1 > Sy2• PEXRAV > SPL• Reflection compatible, large errors• Energy Cut-offs different• Future

Acknowledgements