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Obscured AGN in the COSMOS field

Obscured AGN in the COSMOS field. Andrea Comastri (INAF – Bologna) on behalf of the XMM-COSMOS team. High redshift obscured quasars. Unbiased tracers of SMBH/Host Galaxy “Co-evolution”

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Obscured AGN in the COSMOS field

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  1. Obscured AGN in the COSMOS field Andrea Comastri (INAF – Bologna) on behalf of the XMM-COSMOS team COSMOS Kyoto meeting May 2005

  2. High redshift obscured quasars • Unbiased tracers of SMBH/Host Galaxy “Co-evolution” • Obscured (hard) X—ray emission  SMBH is present and the host galaxy is visible  morphology of obscured AGN • ACF • Interactions COSMOS Kyoto meeting May 2005

  3. Looking for obscured quasars: a combined Xray, optical, near infrared selection ShallowX-ray flux + large area  pick-up the most extreme sources • Selection of high-z obscured QSO: • from X-ray + photo-z catalog • optical-to-near-infrared color (R-K>4) • X-ray-to-optical color (X/O>10) • photometric redshift (zphot>1) (adapted from Brusa et al. 2005) COSMOS Kyoto meeting May 2005

  4. Luminosity vs. column density Spectral analysis of the brightest X-ray sources ~50% are indeed QSO2! adapted from Brusa et al. 2005 COSMOS Kyoto meeting May 2005

  5. X-ray emitting EROs at z~1.4 Average X-ray spectrum NH= 3. 10^22 L(X)= 10^44 The K-brightest objects will be observed with the low resolution IR (JHK) AMICI spectrograph at TNG COSMOS Kyoto meeting May 2005

  6. Morphological test on primary/secondary identifications Most of the counterparts (~80%) of hard sources (undetected in the soft band)are extended (obscured nucleus both in X-ray and optical bands) and “reddish” ( ~60% with R-K>4; to be compared with 25% for the total number of primary IDs) with 0.8 <zphot< 1.8 ( ~ 70%) Excellent consistency between X-ray spectra and optical (ACS + color) data COSMOS Kyoto meeting May 2005

  7. Angular Correlation Function in COSMOS The large connected area should allow the determination of the angular correlation function w(θ) = (θ/θ0)-γ up to a large scale Giacconi et al. 2001 CDFS – 120 ksec Complementary to Chandra data from which w(θ) is well measured for 5 < θ < 100 arcsec: γ ~ 1; θ0 ~ 10 arcsec COSMOS Kyoto meeting May 2005

  8. Chandra (Yang et al. 2003) stronger signal in the hard band Θ (h) ~ 40+-11 Θ (s) ~ 4+-2 115 hard sources 298 soft sources XMM 2dF Shallow Survey (1+1 deg2) Basilakos et al. 2004/2005 Θ (h) ~ 22+-10 Θ (s) ~ 10+-2 171 hard sources 432 soft sources COSMOS Kyoto meeting May 2005

  9. Angular Correlation Function in COSMOS:The Soft Sample Preliminary results on 12 XMM pointings : area ~ 1.3 sq. deg. Applying the Landy-Szalay and the Hamilton estimators (see Kerscher et al. 2000 for a comparison of the most widely used estimators) we find that : Cut due to integral constraint Soft sample (0.5 – 2.0 keV): About 650 sources – Signal for 20 < θ < 1250 arcsec (0.15 < d < 10 Mpc at z ~ 1) γ ~ 0.45 Θ0 ~ 1.5 – 2.0 arcsec ( but based on significant extrapolation …) COSMOS Kyoto meeting May 2005

  10. Angular Correlation Function in COSMOS:The Hard Sample Comparison between Hard and soft ACFs Hard Soft About 310 sources Signal for 40 < θ < 1250 arcsec (0.3 < d < 10 Mpc at z ~ 1) γ ~ 0.55 Θ0 ~ 4 - 5 arcsec COSMOS Kyoto meeting May 2005

  11. Angular Correlation Function in COSMOS:Preliminary conclusions Both soft and hard selected samples show significant correlation from 25 – 40 arcsec up to about 20 arcmin (limit due to the integral constraint) The slopes are somewhat flatter (γ ~ 0.5) than “canonical” values Θ0 values ( ~ 1.5 arcsec (Soft) and ~ 4.5 arcsec (hard) ) are uncertain,but appear to be smaller than in CDFS The hard correlation function is somewhat higher than the soft one, but not yet statistically significant (due to different redshift distribution?) COSMOS Kyoto meeting May 2005

  12. X-ray enhancement due to interactions? Examples of ACS images around X-ray sources : 2” radius Are these objects in interaction? How many do we have in the X-ray sample? COSMOS Kyoto meeting May 2005

  13. X-ray enhancement due to interactions? Preliminary analysis (Vignali et al., in progress) on a sub-sample of XMM sources with an optical identification (~ 125/600 = 21 %) shows that the number of additional ACS sources within 2” is higher than in a comparison sample with the same magnitude distribution as the sample of optical IDs (51 vs 42) The excess of close pairs around X-ray sources is therefore 9 +- 7, not statistically significant, yet (to be completed on the total sample) In any case, this analysis suggests that possible effects relating X-ray enhancement to on-going interactions, if present, are effective for a small fraction (< 10% ?) of the X-ray sources. COSMOS Kyoto meeting May 2005

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