COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
Obscured AGN in the Obscured AGN in the COSMOS fieldCOSMOS field
Andrea Comastri (INAF – Bologna) on Andrea Comastri (INAF – Bologna) on behalf of the XMM-COSMOS teambehalf of the XMM-COSMOS team
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
High redshift obscured quasarsHigh 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 2005COSMOS Kyoto meeting May 2005
Looking for obscured quasars: Looking for obscured quasars: a combined a combined XrayXray, , opticaloptical, , near infrarednear infrared selection selection
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)
Shallow X-ray flux + large area pick-up the most extreme sources
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
Luminosity vs. column densityLuminosity vs. column density
Spectral analysis of thebrightest X-ray sources
~50% are indeed QSO2!
adapted from Brusa et al. 2005
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
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 withthe low resolution IR(JHK) AMICI spectrograph at TNG
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
Morphological test on primary/secondary identificationsMorphological 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 2005COSMOS Kyoto meeting May 2005
Angular Correlation Function in COSMOSAngular 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
Complementary to Chandra data from which w(θ) is well measured for 5 < θ < 100 arcsec: γ ~ 1; θ0 ~ 10 arcsec
Giacconi et al. 2001CDFS – 120 ksec
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
Chandra (Yang et al. 2003) stronger signal in the hard bandΘ (h) ~ 40+-11Θ (s) ~ 4+-2 115 hard sources 298 soft sources
XMM 2dF Shallow Survey (1+1 deg2) Basilakos et al. 2004/2005 Θ (h) ~ 22+-10Θ (s) ~ 10+-2 171 hard sources432 soft sources
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
Angular Correlation Function in COSMOS:Angular Correlation Function in COSMOS:The Soft SampleThe 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 :
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 ~ 0.45Θ0 ~ 1.5 – 2.0 arcsec ( but based on significant extrapolation …)
Cut due tointegralconstraint
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
Angular Correlation Function in COSMOS:Angular Correlation Function in COSMOS:The Hard SampleThe Hard Sample
About 310 sources Signal for 40 < θ < 1250 arcsec(0.3 < d < 10 Mpc at z ~ 1)
γ ~ 0.55Θ0 ~ 4 - 5 arcsec
Hard
Soft
Comparison betweenHard and soft ACFs
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
Angular Correlation Function in COSMOS:Angular Correlation Function in COSMOS:Preliminary conclusionsPreliminary 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 2005COSMOS Kyoto meeting May 2005
X-ray enhancement due to interactions?X-ray enhancement due to interactions?
Are these objects in interaction? How many do we have in the X-ray sample?
Examples of ACS images around X-ray sources : 2” radius
COSMOS Kyoto meeting May 2005COSMOS Kyoto meeting May 2005
X-ray enhancement due to interactions?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.