1. Obscured AGN and XRB models Andrea Comastri (INAF-OABologna-Italy) Roberto Gilli (INAF-OABologna-Italy) F. Fiore (INAF-OARoma-Italy) G. Hasinger (MPE-Garching- Germany) M. Brusa (MPE-Garching-Germany) C. Vignali (Bologna University) R. Della Ceca (INAF-OABrera-Italy) G. Malaguti (INAF-IASFBo-Italy)

2. SimbolX, May 15, 20072 G Deep X-ray surveys have resolved some 80% of the XRB (below a few keV ) but “only” 50% > 6 keV and a few (1-2%) above 10 keV. G Wealth of X-ray and multiwavelength follow- up available -> possible to predict the missing population (Compton Thick AGN) G The missing population may provide an important contribution to the BH mass function SMBH/galaxy evolution, accretion rates, Eddington ratios, … G Deep X-ray surveys have resolved some 80% of the XRB (below a few keV ) but “only” 50% > 6 keV and a few (1-2%) above 10 keV. G Wealth of X-ray and multiwavelength follow- up available -> possible to predict the missing population (Compton Thick AGN) G The missing population may provide an important contribution to the BH mass function SMBH/galaxy evolution, accretion rates, Eddington ratios, …

3. SimbolX, May 15, 20073

4. 4 Frontera+07astro-ph/0611228

5. Model scheme XRB flux “ uncertain ”, so use the more robust constraints below 10 keV (eg. source counts) to lock the properties (eg obs/unobs ratio, N H dist.) of the Compton Thin (log NH < 24) AGN Estimate the Compton Thin/Unobs. Ratio by comparing hard vs. soft XLF. Absorption distribution from X-ray counts. Include continuum slope dispersion. Add Compton thick AGN to fit the 30 keV bump Verify assumptions/make predictions on Compton Thick AGN XRB flux “ uncertain ”, so use the more robust constraints below 10 keV (eg. source counts) to lock the properties (eg obs/unobs ratio, N H dist.) of the Compton Thin (log NH < 24) AGN Estimate the Compton Thin/Unobs. Ratio by comparing hard vs. soft XLF. Absorption distribution from X-ray counts. Include continuum slope dispersion. Add Compton thick AGN to fit the 30 keV bump Verify assumptions/make predictions on Compton Thick AGN

6. SimbolX, May 15, 20076 Unabsorbed: logNH<21 (plus Compton reflection) Compton-Thin: 21<logNH<24 Compton-Thick: logNH>24 Mildly (log NH =24-25) (NGC 6240, Circinus) Heavily (log NH >25) (NGC1068)

7. SimbolX, May 15, 20077 Best fit ratios ~ 4 at low Log Lx < 44 Luminosities ~ 1 at high Log Lx > 44 luminosities

8. SimbolX, May 15, 20078 X-ray logN-logS

9. SimbolX, May 15, 20079 NH distribution Thick T h i n

10. SimbolX, May 15, 200710 G Radio loud AGN / Blazars contribute some 10% to the soft XRB (Galbiati et al 2004; Giommi et al 2006) G Normalizing to 1 keV for a range of slopes (0.5-0.7) a break or cut-off must be present around 1 MeV otherwise the soft-gamma-ray background would be exceeded High energy cut-off 100-400 keV

11. SimbolX, May 15, 200711 hard X-ray surveys still miss the most obscured sources (do not sample the XRB peak) Missing population: (numerous) moderate luminous, log NH > 23, z = 0.5-2 ( Worsley+04,05, AC 04,05 ) and Compton Thick AGN (log NH > 24) Unresolved Background AC 05Worsley+05

12. SimbolX, May 15, 200712

13. 70-75% of The BeppoSAX/ INTEGRAL 10-40 keV XRBResolved

14. SimbolX, May 15, 200714 Obscured AGN fraction vs sample limiting flux Thick All abs.

15. Expected number of sources per SX field Gilli +07 La Franca+05 Della Ceca

16. SimbolX, May 15, 200716 NGC5728 NGC4992 Scattering fraction ~ 2% Scattering fraction < 0.5 % See also Wilman et al. 2002 HyLIG SUZAKU OBSERVATION OF Mildly CT nearby galaxies AC+07 (astro-ph/0704.1253)

17. SimbolX, May 15, 200717 4 X

18. Heavily Thick will not be well sampled by deep hard X-ray Surveys

19. SimbolX, May 15, 200719 Local Black Holes and AGN relics Marconi et al. 2004 have shown that local BHs are relics of AGN activity by comparing: the local BH mass function (from galaxy L/ σ functions and M BH - L bul /M BH - σ e ) the relic BHMF (from AGN luminosity function and continuity equation) Importance of AGN LF: even the hard (2-10 keV) XLF does not sample the whole AGN population. Heavily obscured Compton- thick AGN are missing... Marconi et al. 2004 have shown that local BHs are relics of AGN activity by comparing: the local BH mass function (from galaxy L/ σ functions and M BH - L bul /M BH - σ e ) the relic BHMF (from AGN luminosity function and continuity equation) Importance of AGN LF: even the hard (2-10 keV) XLF does not sample the whole AGN population. Heavily obscured Compton- thick AGN are missing... Qso LF Hard-X LF Soft-X LF

20. SimbolX, May 15, 200720 G Correction for Compton-Thick sources from XRB models  whole AGN pop considered G The only free parameters are the accretion efficiency and Eddington ratio L = ε dM/dt c 2 L = λ L Edd

21. SimbolX, May 15, 200721 Radiative Efficiency and Fraction of Eddington luminosity Effect of changing scattering efficiency to compute pure reflection spectra of Compton- Thick sources 2% 0.5% 10%   Determine locus in ε - λ plane where there is the best match between local and relic BHMF!   ε =0.04-0.10 λ =0.08-0.5 which are consistent with common ‘beliefs’ on AGNs   Determine locus in ε - λ plane where there is the best match between local and relic BHMF!   ε =0.04-0.10 λ =0.08-0.5 which are consistent with common ‘beliefs’ on AGNs CT space density degenerates with accretion efficiency and geometry of reflecting thick matter …

22. SimbolX, May 15, 200722 Obscured AGN and SMBH census: observation strategies 1. A spectral survey of local CT Seyfert 2 galaxies previously discovered by BeppoSAX, INTEGRAL Swift and Suzaku. This should be accompanied by a volume limited survey of IR-bright or OIII-bright or … galaxies which have not shown strong X-ray emission below 10 keV, to search for highly CT objects. 2. A spectral survey of moderately obscured luminous QSOs discovered by XMM, Chandra up to z~1 (High luminosity) 3. Deep observations to search for faint mildly CT AGN + serendipitous survey (high redshift) 4. A survey of candidate CT AGN selected using their infrared emission (Spitzer/Herschel). 1. A spectral survey of local CT Seyfert 2 galaxies previously discovered by BeppoSAX, INTEGRAL Swift and Suzaku. This should be accompanied by a volume limited survey of IR-bright or OIII-bright or … galaxies which have not shown strong X-ray emission below 10 keV, to search for highly CT objects. 2. A spectral survey of moderately obscured luminous QSOs discovered by XMM, Chandra up to z~1 (High luminosity) 3. Deep observations to search for faint mildly CT AGN + serendipitous survey (high redshift) 4. A survey of candidate CT AGN selected using their infrared emission (Spitzer/Herschel).

23. Summary A large fraction of the 10-40 keV XRB (2/3 - 3/4) will be resolved at a limiting flux of ~ 6 x 10 -15 cgs A major breaktrough is foreseen (compare with ROSAT and Chandra better than ASCA and BeppoSAX) A large population of CT AGN (as large as Cthin ?) is waiting to be discovered by sensitive hard ( > 10 keV) X- ray observations Statistically meaningful sample of the most obscured AGN over a broad range of fluxes and luminosities -> XLF and evolution, SMBH assembly and distribution, geometry of obscuring/reflecting gas, … A large fraction of the 10-40 keV XRB (2/3 - 3/4) will be resolved at a limiting flux of ~ 6 x 10 -15 cgs A major breaktrough is foreseen (compare with ROSAT and Chandra better than ASCA and BeppoSAX) A large population of CT AGN (as large as Cthin ?) is waiting to be discovered by sensitive hard ( > 10 keV) X- ray observations Statistically meaningful sample of the most obscured AGN over a broad range of fluxes and luminosities -> XLF and evolution, SMBH assembly and distribution, geometry of obscuring/reflecting gas, …