Hard X-ray AGN and the Cosmic X-ray Background

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1 Hard X-ray AGN and the Cosmic X-ray Background Sergey Sazonov Space Research Institute, Moscow, Russia 1 Rome, Oct. 17, 2013

2 Plan Cosmic X-ray background: measurements, modeling and implications for heavily obscured AGN Properties of the local AGN population: hard X-ray infrared connection, observed and intrinsic fraction of strongly absorbed sources Conclusions and implications for future observations Rome, Oct. 17,

3 CXB = integrated emission of AGN Uncertainties in modeling: CXB spectrum AGN spectral shape AGN redshift evolution CT AGN Gilli et al A lot of Compton-thick quasars needed? Rome, Oct. 17,

4 CXB-Earth observations by INTEGRAL in 2006 Churazov et al. 2007

5 Revnivtsev et al. 2003, Churazov et al. 2007

6 Ajello et al. 2008

7 Moretti et al. 2009

8 Updated CXB modeling Akylas et al Treister et al Substantial contribution from Compton-thick sources is not evident Rome, Oct. 17,

9 Average hard X-ray spectrum of local AGN 11 AGN S=AE -1.62±0.03 e -E/(240±30)keV S=AE -1.73±0.09 e -E/(240±100)keV 7-year INTEGRAL sample (Krivonos et al. 2010) Simple stacking: S=Σf i 20 AGN S=AE ±0.11 e -E/(88±20)keV 120 AGN Sazonov et al. 2008, Sazonov et al. 2010

10 Space density-weighted sum: S=ΣL i /V max,i We thus determine both the spectral shape and the total volume emissivity of the local AGN S=AE S=AE e-e/120 kev Red. χ 2 =2.05 (4 dof) 1.03 (3 dof) Sazonov et al. 2008, Sazonov et al. 2010

11 Evolution of AGN X-ray luminosity density Chandra Barger et al. 2005

12 Convolution of local AGN spectrum with z-dependence CXB ε ~ 1/z at z>1 ε = const at z>1 Consistent (within large uncertainties) with the CXB spectrum

13 Ricci et al Vasudevan et al Rome, Oct. 17,

14 What would we like to know about AGN? Accretion physics Distribution of energy between accretion disk and hot corona What is the torus? Opening angle, optical depth, physical size History of supermassive black hole growth Rome, Oct. 17,

15 Тор Диск Корона Bolometric luminosity is distributed between: Medium IR Optical UV (Type 1 AGN) X-ray gamma SS, Ostriker & Sunyaev 2004 Problems: Peak of energy release is in the far UV: absorption along the line of sight Variability: non-simultaneity of observations in different energy bands Rome, Oct. 17,

16 AGN statistics N H We would like to fill this space z L bol Hard X-ray and mid-ir surveys are the best Rome, Oct. 17,

17 AGN studies in the local Universe: INTEGRAL all-sky survey (17-60 kev) 3.5-year survey ( ): 68 Seyferts and QSOs ( b >5 o ) Krivonos 2007; Sazonov et al. 2007, year survey ( ): 150 Seyferts and QSOs ( b >5 o ) Krivonos 2010a, 2010b; Sazonov et al Rome, Oct. 17,

18 Hard X-ray luminosity function z<0.1 z>0.1 All: Log(L * )=43.56±0.18 γ 1 =0.81±0.11, γ 2 =2.28±0.14 z<0.1: Log(L * )=43.76±0.19 γ 1 =0.88±0.11, γ 2 =2.74±0.37 Rome, Oct. 17,

19 Absorption column distribution 45% - unabsorbed (N H <10 22 ) 46% - weakly absorbed (10 22 < N H < ) 9% - strongly absorbed (N H >10 24 ) Rome, Oct. 17,

20 Fraction of obscured AGN as a function of luminosity Receding torus? Ω Torus /4π (log L kev -41.5) Rome, Oct. 17,

21 Swift/BAT 3-year survey Burlon et al Rome, Oct. 17,

22 IR observations of AGN from the 3.5- year INTEGRAL survey AGN AGN + starburst Spitzer Sazonov et al Rome, Oct. 17,

23 Correlation between hard X-ray and mid-ir emission INTEGRAL-Spitzer 68 AGN at z < 0.1 L MIR ~ L HX 0.74±0.06 Rome, Oct. 17,

24 Disk vs. Torus Torus solid angle decreases with luminosity: Ω Torus /4π (log L HX ) (IR) Luminosity of the torus: L Torus = (Ω Torus /4π) L Disk (UV) luminosity of the disk: L Disk = (4π/Ω Torus ) L Torus Rome, Oct. 17,

25 Disk vs. Corona L Disk 1.6 L Corona 0.97±0.06 Thus, the luminosities of disk and corona are similar Rome, Oct. 17,

26 Bolometric corrections Hard X-ray luminosity is a good proxy of the bolometric luminosity for AGN with L kev ~ to erg/s: L bol 10 L kev Hence, absorption corrected X-ray luminosity is a good proxy too: L bol ~ 10 L 2-10 kev Mid-infrared luminosity: L bol ~ 5 L 15 μm but there is a non-linear dependence Rome, Oct. 17,

27 Fraction of heavily obscured AGN =? Compton-thick sources Rome, Oct. 17,

28 Heavily obscured AGN in the INTEGRAL sample IGR J =ESO 137-G34 XMM IBIS Using X-ray data for such objects, one can estimate N H or show that N H > (reflection dominates) Malizia al Rome, Oct. 17,

29 Propagation of hard X-rays through Torus Rome, Oct. 17,

30 AGN-1 AGN-2 Rome, Oct. 17,

31 Observed flux as a function of direction and N H Rome, Oct. 17,

32 Average influence on AGN-1 and AGN-2 luminosities AGN-1 AGN-2 Rome, Oct. 17,

33 True (absorption-corrected) hard X-ray luminosity function of local AGN Assumptions: Torus opening angle θ=45 o In AGN-1s, N H =10 24 Two main effects : AGN-1 (67) move to the left Heavily obscured AGN-2 (13) move to the right Emitted luminosity Each AGN gives its own estimate of AGN space density (1/V max ) -> large errors Rome, Oct. 17,

34 Intrinsic dependence of obscured AGN fraction (torus opening angle) on luminosity Rome, Oct. 17,

35 Perhaps, no discrepancy with IR/radio selected samples? Lawrence & Elvis 2010 Rome, Oct. 17,

36 Conclusions Cosmic X-ray background does not provide stringent constraints on the abundance of heavily obscured AGN in the Universe Hard X-ray luminosity of the hot corona is comparable to the UV luminosity of the accretion disk in AGN > constraints on accretion models Hard X-ray luminosity is a good proxy of AGN bolometric luminosity -> good for reconstructing SMBH growth history using large surveys Measured fraction of absorbed AGN decreases with luminosity > indication of increasing opening angle of the torus However, when corrected for the observational bias, the fraction of obscured AGN does not show significant dependence on luminosity We need larger samples of hard X-ray selected AGN perhaps in combination with mid-ir data Rome, Oct. 17,

37 Rome, Oct. 17,

38 Hasinger 2008 Rome, Oct. 17,

39 Rome, Oct. 17,

Hard X-ray selected sample of AGN: population studies

Hard X-ray selected sample of AGN: population studies Angela Malizia INCREASE OF AGN POPULATION IN THE INTEGRAL SURVEYS most of the unidentified objects have been subsequently classified as AGN Many more