The Evolution of AGN Obscuration

1. The Evolution of AGN Obscuration Ezequiel Treister (ESO) Meg Urry (Yale) Julian Krolik (JHU) Shanil Virani (Yale) Priya Natarajan (Yale)

2. Host Galaxy Active Galactic Nucleus (AGN) supermassive black hole actively accreting matter 1-1000 x galaxy luminosity from few lt-hrs

3. broad lines blazars, Type 1 Sy/QSO The AGN Unified Model Urry & Padovani, 1995

4. radio galaxies, Type 2 Sy/QSO narrow lines The AGN Unified Model Urry & Padovani, 1995

5. Supermassive Black Holes Many obscured by gas and dust • How do we know that? • Local AGN Unification • Explain Extragalactic X-ray “Background” Credit: ESO/NASA, the AVO project and Paolo Padovani

6. Observed X-ray “Background” Frontera et al. (2006)

7. AGN in X-rays Photoelectric absorption affect mostly low energy emission making the observed spectrum look harder. Increasing NH

8. X-ray Background XRB well explained using a combination of obscured and unobscured AGN. # w NH > 1023 cm-2 still uncertain. • Setti & Woltjer 1989 • Madau et al. 1994 • Comastri et al. 1995 • Gilli et al. 1999,2001 • And others… Treister & Urry, 2005

9. What do we know so far? • More obscured AGN at low luminosity (Steffen et al. 2003, Ueda et al. 2003, Barger et al. 2005, Akylas et al. 2006) • More obscured AGN at high-z? (Ueda et al. 2003: No, La Franca et al. 2005: yes, Ballantyne et al. 2006: yes) • Problems: • Low number of sources • Selection effects: • - X-ray selection (missed obscured sources) • - Optical incompleteness (no redshifts) • - X-ray classification: “K correction”

10. Meta-Survey • 7 Surveys, • 2341 AGN, 1229 w Ids • 631 Obscured • (no broad lines) • 1042<Lx<1046, 0<z<5 Treister & Urry, 2006

11. Total effective area of meta-survey Treister & Urry, 2006

12. Ratio vs Redshift Treister & Urry, 2006

13. Ratio vs Redshift Treister & Urry, 2006

14. Ratio vs Redshift Treister & Urry, 2006

15. Ratio vs Redshift Key input: Luminosity dependence of obscured AGN fraction. See also: La Franca et al. 2005 Ballantyne et al. 2006 Akylas et al. 2006 Treister & Urry, 2006

16. Ratio vs Luminosity Treister & Urry, 2006

17. Ratio vs Luminosity Treister & Urry, 2006

18. Ratio vs Luminosity Hasinger et al. Treister & Urry, 2006

19. The AGN Unified Model Urry & Padovani, 1995

20. ~2x A Changing Torus? A change in the IR/NUV flux ratio may indicate a change in torus geometry. Granato & Danese Torus model

21. Low L • GOODS: North+South fields • 10 unobscured AGN • All Spitzer 24 µm photometry • 8 with GALEX UV data • High L • SDSS DR5 Quasar sample • 11938 quasars, 0.8<z<1.2 • 192 with Spitzer 24 µm photometry • 157 of them with GALEX UV data Torus StructureSample • Completely unobscured AGN • Narrow redshift range, 0.8<z<1.2 • Wide range in luminosity • Data at 24 µm from Spitzer • Mid L • COSMOS • 19 unobscured AGN • 14 Spitzer 24 µm photometry • All with GALEX UV data

22. Torus Structure Bolometric luminosity constructed from NUV to mid-IR. No change in NUV/Bol ratio with luminosity! Treister et al, ApJ submitted.

23. Torus Structure Change in 24 µm/Bol ratio with luminosity! • Lower ratio at high L • Consistent with larger opening angles at higher luminosities. Treister et al, ApJ submitted.

24. Fraction of Obscured AGN Similar luminosity dependence as found on X-ray surveys. • Higher values from • fIR/fbol method. • Obscured AGN • missed by X-ray • surveys. Detected • in mid-IR? Treister et al, ApJ submitted.

25. HST ACS color image (0.3% of GOODS)

26. HST+Spitzer color image (0.3% of GOODS)

27. IR Fraction vs Flux AGN are bright IR sources! Treister et al 2006

28. IR Luminosity Distribution On average, AGN are ~10x brighter than normal galaxies For fainter AGN, the host galaxy makes a significant contribution Treister et al 2006

29. Infrared Background AGN (+ host galaxy) contribute ~3-10% of the total extragalactic background light Treister et al 2006

30. Compton Thick AGN • Defined as obscured sources with NH>1024 cm-2. • Very hard to find (even in X-rays). • Observed locally and needed to explain the X-ray background. • Number density highly uncertain. • High energy (E>10 keV) observations are required to find them.

31. INTEGRAL Survey • PIs: MegUrry, ShanilVirani, Ezequiel Treister • Exp. Time (Msec): 0.7 (archive)+1.5 (2005)+ 1 (2008). Deepestextragalactic INTEGRAL survey • Field: XMM-LSS (largestXMM field) • Flux limit: ~4x10-12ergs cm-2 s-1(20-40 keV) • Area: ~1,000 deg2 • Sources: ~20 • Obscured AGN: ~15 (~5 Compton-thick)

32. MCG-02-08-014 INTEGRAL Mosaic (2.2 Ms) Significance Image, 20-50 keV

33. MCG-02-08-014 • z=0.0168 • Optical class: Galaxy • IR source (IRAS) • Radio source (NVSS) • Narrow line AGN • (based on OIII emission) • No soft X-rays (ROSAT) • Good CT AGN candidate

34. INTEGRAL AGN logN-logS Data points from Beckmann et al. 2006 Treister et al, submitted

35. Space Density of CT AGN X-ray background does not constrain density of CT AGN Treister et al, submitted

36. Treister & Urry, 2005 CT AGN and the XRB XRB Intensity HEAO-1 +40% Treister et al, submitted

37. Treister & Urry, 2005 Gilli et al. 2007 CT AGN and the XRB XRB Intensity HEAO-1 Original HEAO-1 +10% HEAO-1 +40% Treister et al, submitted

38. Treister & Urry, 2005 Gilli et al. 2007 Most likely solution CT AGN Space Density CT AGN and the XRB XRB Intensity HEAO-1 Original HEAO-1 +10% HEAO-1 +40% Treister et al, submitted

39. X-ray Background Synthesis Treister & Urry 2005

40. X-ray Background Synthesis Treister & Urry 2005

41. Summary • AGN unification can account well for the observed properties of the X-ray background. • The obscured AGN fraction decreases with increasing luminosity. • Ratio of IR to Bolometric luminosity in unobscured AGN suggest this is due to a change in opening angle. • The obscured AGN fraction increases with redshift as (1+z)0.4. • AGN are luminous infrared sources, but contribute ~5% to extragalactic infrared background • Survey at high energies starts to constrain the spatial density of CT AGN.