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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

Obscured AGN in the COSMOS field

Andrea Comastri (INAF – Bologna) on behalf of the XMM-COSMOS team

COSMOS Kyoto meeting May 2005

high redshift obscured quasars
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

slide3

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

luminosity vs column density
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

x ray emitting eros at z 1 4 average x ray spectrum
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

morphological test on primary secondary identifications
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

angular correlation function in cosmos
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

slide8

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

angular correlation function in cosmos the soft sample
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

angular correlation function in cosmos the hard sample
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

angular correlation function in cosmos preliminary conclusions
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

x ray enhancement due to interactions
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

x ray enhancement due to interactions1
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