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X-ray spectroscopy of bright AGN GiorgioMatt & Stefano Bianchi Giorgio Matt & Stefano Bianchi (Dipartimento di Fisica, Università Roma Tre) (Dipartimento.

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Presentation on theme: "X-ray spectroscopy of bright AGN GiorgioMatt & Stefano Bianchi Giorgio Matt & Stefano Bianchi (Dipartimento di Fisica, Università Roma Tre) (Dipartimento."— Presentation transcript:

1 X-ray spectroscopy of bright AGN GiorgioMatt & Stefano Bianchi Giorgio Matt & Stefano Bianchi (Dipartimento di Fisica, Università Roma Tre) (Dipartimento di Fisica, Università Roma Tre)

2 Bright AGN With bright AGN I mean sources with enough photons to allow for a decent spectral analysis in the 0.2-4 (0.1-6) keV energy range About 60000 AGN with more than 5000 counts WFXT (0.5-2 keV) will be detected by WFXT Population studies over very wide ranges of the main parameters will be possible Optical coverage (SLOAN, etc) of the same fields will provide parameters like the mass of the BH

3 Some open problems (which can be addressed by WFXT) The nature of the soft X-ray emission in unobscured sources The properties of the warm absorber beyond the local Universe The IT effect at high z (>1) and L

4 The nature of the soft excess The soft X-ray excess was first discovered in the EXOSAT spectrum of Mkn 841 (Arnaud et al. 1985). The thermal disc interpretation of the soft excess has problems: the derived temperatures are too high and always the same (T  M -1/4 ). WFXT WFXT will stretch considerably the range of masses probed. Its soft X-ray band will be also very useful. Mkn 841 (Petrucci et al. 2007)

5 The warm absorber beyind the LU Evidence for warm absorption in 50% of Seyferts. Usually outflowing (v ~ hundreds km/s). Location, mass and energetics largely unknown. WFXT Dependence of ξ on L, Z, BH mass ???  WFXT !! Blustin et al. 2005

6 The IT effect log(EW Fe )=(1.73±0.03) + (-0.17±0.03) log(L X,44 ) Bianchi et al. 2007 The Iwasawa-Taniguchi (a.k.a. X-ray Baldwin) effect is the anticorrelation between the EW of the iron line (narrow core) and the X-ray luminosity (first discovered by Iwasawa & Taniguchi 1993)

7 The IT effect The IT effect may be due to a decrease with L of the covering factor of the reflecting matter (a similar effect has been found by Maiolino et al. 2007 using infrared data). log(EW Fe )=(1.73±0.03) + (-0.17±0.03) log(L X,44 ) Bianchi et al. 2007

8 The IT effect Bianchi et al. 2007 log(EW Fe )=(1.61±0.05) + (-0.19±0.05) log(L bol/Edd ) The anti-correlation of the EW with the Eddington ratio is highly significant

9 The IT effect log(EW Fe )=(1.73±0.04) + (-0.07±0.04) log(L BH,8 ) No significant dependence of the iron EW on the BH mass is instead found

10 The IT effect This effect is not well known at high luminosities and it is probed only in the local Universe. WFXT can expand enormously the range of L and of z probed. Of course, the local Universe is forbidden…

11 Waiting for WFXT… where we are now The XMM-Newton Bright Serendipitous Survey (Della Ceca et al. 2004; Caccianiga et al. 2008): Flux-limited sample (~7x10 -14 erg/s/cm2 in the 0.5-4.5 keV energy range) 400 sources (80% AGN) X-ray selection X-ray selection! Elusive AGN, etc. Caccianiga et al. 2007 Type 2 Type 1

12 Waiting for WFXT… where we are now CAIXA (Catalogue of AGN In the XMM-Newton Archive) is a catalogue of pointed XMM observations of AGN in the public archive up to March 2007 (Bianchi et al. 2009) To be included in CAIXA, a source must have at least 200 (0.5-2 keV) + 200 (2-10 keV) counts In practice, most sources have more than a thousand counts. Biased towards well-known sources. Undefined selection.

13 CAIXA A Catalogue of AGN in the XMM- Newton Archive 156 sources All radio-quiet AGN in targeted XMM-Newton pn observations: >200 counts in either of the (rest-frame) bands of 0.5-2 and 2-10 keV <1% pileup log(R)<1 (quasar) – log(R)<2.4 and log(R X )<-2.755 (Seyfert) ‏ N H <2x10 22 cm -2 6 and 20 cm fluxes (~100% of the catalog) ‏ Hβ FWHM (64% of the catalog) ‏ : only from BLR ( narrow-line objects) BH mass (52% of the mass) ‏ Luminosity dependent bolometric correction (Marconi et al. 2004) ‏ Bianchi et al. 2009

14 General properties ≈-0.8 90 % with z<1 Sy QSO

15 Powerlaw index The average 2-10 keV spectral index for the whole catalogue is 1.73±0.04, with a large spread of σ = 0.45±0.03 Γ steeper in quasars (1.80±0.05, consistent with PG quasars: Piconcelli et al., 2005) than in Seyferts (1.66±0.05). A Kolmogorov-Smirnov test yields that the two populations are different at the 99% level The difference is even larger if we consider narrow-line objects (1.94±0.07) with respect to broad-line objects (1.62±0.04). In this case, a K- S test gives a NHP of 2x10 -5 It is important to stress here that the photon indexes in CAIXA, in principle, are not the intrinsic ones, because we do not include a Compton reflection It is possible that the different photon indexes found for different populations in CAIXA do not only (or at all) reflect differences in the intrinsic Γ of the sources, but also in the amount of Compton reflection BLS1 NLS1

16 Soft excess Hβ FWHM is correlated with the hard X-ray luminosity and anti-correlated with the ratio between the optical V and the X-ray flux Objects with narrow-lines seems to be X-ray weaker than broad-line objects

17 Soft excess If we replace the second power law with a thermal model, the soft excess in unobscured radio-quiet AGN is characterized by a temperature which is constant across the range of luminosities and BH masses, as already shown by several authors (Gierlinski & Done 2004; Crummy et al. 2006) 123 out of 156 sources need a second and steeper powerlaw to model the soft X-ray emission

18 Correlations with BH mass The strong correlation between the X-ray luminosity and the BH mass has a slope flatter than 1, suggesting that high- luminosity objects may be X-ray weak A luminosity dependent bolometric factor could explain this result, but the one proposed by Marconi (2004) leads to a more-than-linear relation Interestingly, a linear relation is recovered using a bolometric correction based on mdot (Vasudevan & Fabian 2008) or using the radio luminosity

19 The iron lines The average EW of the neutral (narrow) Kα iron line is around 80 eV, as expected for Type 1 objects. And, as said before, we confirmed the IT effect! We do not find different rates of detection for ionised iron lines for narrow- and broad-line objects

20 The iron lines Both the Fe XXV and Fe XXVI lines are detected in 24 sources Their EWs and the ratios between them are consistent with a production in distant matter photoionised by the AGN, with large ionization parameters and large column densities (up to 10 23 cm -2 for Fe XXV, larger for FeXXVI) We cannot exclude a contribution from an ionised accretion disc for the larger EWs

21 Conclusions XMM-Newton Thanks to XMM-Newton we have a decent idea of the X-ray average properties of (unobscured) AGN in the Local Universe. WFXT WFXT will extend this to high luminosities and redshifts


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