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The X-ray view of absorbed INTEGRAL AGN

Explore the X-ray and gamma-ray properties of absorbed AGNs, with detailed analysis of spectral features and gas absorption. Utilize data from INTEGRAL satellite and other telescopes to investigate nature and geometry of absorbing and reflecting gas.

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The X-ray view of absorbed INTEGRAL AGN

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  1. A. De Rosa On behalf of the INTEGRAL/AGN survey team The X-ray view of absorbed INTEGRAL AGN

  2. INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) Astronomical satellite for observing the gamma-ray sky launched on October 17, 2002 The imager IBIS(Imager on Board the INTEGRAL Satellite) IBIS achieves an angular resolution of 12 arcmin over an energy range between 15 keV and 200 keV in the case of ISGRI (Integral Soft Gamma-Ray Imager)

  3. 3 survey provided so far, 4th on-goinghttp://www.integral.soton.ac.uk/projects/ibis_survey/data_access/access.html 40000pointed science windows 63 Ms 2nd catalogue (209 sources) + 1st HE catalogue (2006) 1st catalogue (2005) 126 sources 3rd catalogue (2007) 421 sources 4th LE and 2nd HE catalogue on going Spans a duration of IJD = 1052 - 2688 1600+ days

  4. The sky according to IBIS AGN distribution (131 sources)

  5. Optical spectroscopy of most likely counterparts http://www.iasfbo.inaf.it/extras/IGR/main.html Telescopes: Loiano-Bologna Italy, South Africa, CTIO-Chile, La Silla Chile, CASLEO Argentina Sey1 Narrow-Line Sey1 Masetti et al. 2004, 2006 2008 A first catalogue of 60 AGN (Bassani et al. 2006) 82% Seyferts Sey2/Sey1=1 Gamma ray selection favours broad line sources X-ray bright optically dull AGN Sey2

  6. The IBIS complete sample of AGNs The IBIS AGN total sample: 131 objects 58 type 1 (circles) 60 type 2 (squares) 13 blazars (triangles) + 21 AGN candidates The INTEGAL AGN complete sample 74 objects: 36 type 1 30 type 2 8 blazars/QSO

  7. Broad-band observationsCharacterization of X-ray/gamma-ray spectra Primary Objectives: • Measurement of the column density • Definition of the primary (Γ, Cut-off energy and Reflection) • Secondary Objective: • study other source features (soft X-ray excess, soft emission lines) X-ray Observations:SWIFT-XRT Chandra XMM (AO4, AO5, current AO C approved targets) ASCA BeppoSAX/MECS Gamma-ray Observations:INTEGRAL (IBIS) BeppoSAX (PDS), when available

  8. INTEGRAL type 1 Seyferts: sample selection(Panessa et al. 2008) • Sample of type 1 and 1.5 Seyfert galaxies with F(20-100 keV) > 5 mCrab • New XMM-Newton data (AO3/AO4) • first data below 10 keV with this high sensitivity • Nearby sources with z<0.054 • Representative of the INTEGRAL type 1 AGN population

  9. INTEGRAL Type 2 Seyferts: sample selection(De Rosa et al. 2008) • Absorbed objects i.e. NH>1022 cm-2 • Type 2 AGN with F(20-100 keV) < 5 mCrab • We excluded sources with broad-band data already studied by BeppoSAX • One well known source was retained (even if already studied by BeppoSAX) as a posteriori check for our analysis that is affected by limitation of using non simultaneous X and soft-gamma rays measurements Our sample is representative of the populations of type 2 AGN observed by INTEGRAL above 10 keV

  10. IGR J10404-4625 Nature/geometry of the absorbing gas type 2 vs type 1 objects CXRB synthesis study Compton thick vs Compton thin sources Nature/geometry of the reflecting gas Geometry at few Rg from the SMBH: AD? WSM? Thermal vs scattered scenario Broad band observations: the physics geometry of innermost regions of AGN Absorption: NH Spectral slope and high energy cut-off: , Ec Iron line together with the Compton reflection hump: EW, R,AFe Soft X-ray excess: kT, Asc/AIC

  11. NH galactic NH intrinsic 37 < 22 36 > 22 ~50% BAT 55% The NH distribution in the overall sample

  12. NH galactic NH intrinsic 3 unabsorbed Sy2s: IGR J12415-5757 IGR J16024-6107 IGR J16351-5806 The NH distribution: type 1 vs type 2

  13. SAX average values The Compton reprocessing components I. The Reflection Hump Test the correlation between the photon index and R as proposed by Zdziarski et al. (1999) .. hard to check! Possible with the larger sample Correlation factor r=0.0709 Is the absorbing gas (the torus) able to produce the observed reflection hump? • For NH ~1023-1024-1025 cm-2 the contribution of the torus at the flux at 30 keV is 8, 29 and 55 per cent respectively (Ghisellini et al. 1994). • Value of R higher than 2 can be 2 “real” or due to low flux state of the source or miscalibration between X-ray and gamma-ray instruments • Cross-calibration constant measuerments on stable source (Crab) suggests C=1 at 20 keV for INTEGRAL/XMM-Chandra-ASCA (Kirsch et al. 2005)

  14. SAX SAX The Compton reprocessing components: II. The iron line observations The lines are due to cold iron and with narrow profile <0.3 keV If the line is produced far away the central source (TORUS?), at higher NH the continuum photons will be absorbed BUT not the line photons => increasing the EW The NH values we found are in 4-40 1022 cm-2 would produce EW(Fe)=10-200 eV.

  15. The origin of the Compton reflection features Question:Is this component produced in the absorbing medium? R and EW are too high to be produced in the absorber with the measured NH Solution:the absorber is not homogeneous and the thick medium covers a large fraction of the solid angle but not the line of sight (already proposed by Risaliti et al. 2002). Clumpy torus The alternative scenario: a grazing incidence of the intrinsic continuum on the inner edge of the torus: the high-energy photons

  16. Reflected continuum & Fe line NLR scattered-thermal component Comptonizedcontinuum torus =100 Cold thick disc The sketch: a “grazing incidence” reflection

  17. SAX IC 4518A NGC 788 The intrinsic continuum: vs Ec • All the values of Ec we measure (even if lower limits) suggest that this feature is a common property of Seyfert galaxies. • In a pair of AGN the photon index is flatter than the average observed in Seyfert. Also including type 1 INTEGRAL AGN (Panessa et al. 2008). This evidence can be or “real” (as expected in the CXRB synthesis model, Gilli et al. 2007) or to the presence of complex absorption An anti-correlation between photon index and Ec is expected in a Comptonizzation model (Haardt et al. 1997).. hard to check. Possible with larger sample and deep observations

  18. IBIS SPECTRA 15-100 keV preliminary… Photon index distribution of type 1 & 2 (59 objects) Weighted Mean <>=2.01±0.01 <> BAT =2.00±0.07

  19. <>=2.06±0.02 Photon index distribution: type 1 vs type 2 <>=1.96±0.02 BAT: <> =1.86±0.10 <> =2.07±0.02 BAT: <> =2.23±0.11 Sey 2s have harder X-ray spectra than Sey 1s BUT

  20. Conclusions    We presented the broad-band study of absorbed INTEGRAL AGN with the main goal to investigate the properties of theabsorption/reflection and the intrinsic continuum characterization Compton reprocessing components (R & Fe line) tell us that the reflection/absorbing medium can be one and the same even if with some particular constraint (not homogeneous, grazing incidence). ... but variability studies can help to investigate a different scenario: R vs flux relation. Link the iron line properties with the reflection The value of the high energy cut-off we found suggests that it is a common property of Type 1 and Type 2 broad line AGNs ...but correlations gamma vs flux, gamma vs Ecut-off have to be checked The fraction of absorbed/unabsorbed sources is ~50%, in agreement with BAT results …but highly absorbed AGNs (SAX results by Risaliti 1999) are missing in our sample

  21. What we need now? • Variability studies (that we completely miss in this analysis) need very deep INTEGRAL observations joint to multi-wavelength campaign with XMM, Chandra and Swift. • INTEGRAL extragalactic fields are now available (2Ms on NEP) & the 4th cat/survey will double the number of AGN detected. This will allow us to build a larger sample to search for correlations and variability study.

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