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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)

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Obscured AGN and XRB models

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  1. 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) Obscured AGN and XRB models

  2. 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. • Wealth of X-ray and multiwavelength follow-up available -> possible to predict the missing population (Compton Thick AGN) • The missing population may provide an important contribution to the BH mass function SMBH/galaxy evolution, accretion rates, Eddington ratios, … SimbolX, May 15, 2007

  3. SimbolX, May 15, 2007

  4. Frontera+07 astro-ph/0611228 SimbolX, May 15, 2007

  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, NH 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. 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) SimbolX, May 15, 2007

  7. Best fit ratios ~ 4 at low Log Lx < 44 Luminosities ~ 1 at high Log Lx > 44 luminosities SimbolX, May 15, 2007

  8. X-ray logN-logS SimbolX, May 15, 2007

  9. NHdistribution Thick T h i n SimbolX, May 15, 2007

  10. Radio loud AGN / Blazars contribute some 10% to the soft XRB (Galbiati et al 2004; Giommi et al 2006) • 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 SimbolX, May 15, 2007

  11. Unresolved Background AC 05 Worsley+05 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) SimbolX, May 15, 2007

  12. SimbolX, May 15, 2007

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

  14. Obscured AGN fraction vs sample limiting flux All abs. Thick SimbolX, May 15, 2007

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

  16. SUZAKU OBSERVATION OF Mildly CT nearby galaxies AC+07 (astro-ph/0704.1253) Scattering fraction < 0.5 % NGC5728 Scatteringfraction ~ 2% See also Wilman et al. 2002 HyLIG NGC4992 SimbolX, May 15, 2007

  17. 4 X SimbolX, May 15, 2007

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

  19. Local Black Holes and AGN relics Hard-X LF • 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 MBH-Lbul/MBH-σe) • 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 ... Soft-X LF Qso LF SimbolX, May 15, 2007

  20. Correction for Compton-Thick sources from XRB models  whole AGN pop considered • The only free parameters are the accretion efficiency and Eddington ratio L = ε dM/dt c2 L = λ LEdd SimbolX, May 15, 2007

  21. Radiative Efficiency and Fraction of Eddington luminosity • 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 • Effect of changing scattering efficiency to compute pure reflection spectra of Compton-Thick sources CT space density degenerates with accretion efficiency and geometry of reflecting thick matter… 2% 0.5% 10% SimbolX, May 15, 2007

  22. Obscured AGN and SMBH census:observation strategies • 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. • A spectral survey of moderately obscured luminous QSOs discovered by XMM, Chandra up to z~1 (High luminosity) • Deep observations to search for faint mildly CT AGN + serendipitous survey (high redshift) • A survey of candidate CT AGN selected using their infrared emission (Spitzer/Herschel). SimbolX, May 15, 2007

  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, …

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