Boston, November 2006Extragalactic X-ray surveys

Paolo Tozzi

Spectral analysis of X-ray sources

in the CDFS

0.3-1 keV

1-3 keV

3-7 keV

Rosati et al. 2002

National Geographic, Dec 2002

Detailed spectral analysis of X-ray sources

Tozzi, Gilli, Mainieri et al. 2006, A&A, 451, 457

Deep X-ray Surveys: some open issues

The distribution of intrinsic absorption among AGN

Detection of Compton-Thick AGN

The unresolved fraction of the XRB at high energies

Compton thick candidates

NH vs redshifts for the whole sample

Detected fraction as a function of NH and z

Sampling different luminosity and spectral population at different zSelection effects are relatively easy to model in the X-ray band

z < 0.7

0.7 < z <1.5

z > 1.5

NH histogram corrected for completeness

Corrected for completenessand sources outside the detectability region

<log(NH)> ~ 23.1

dispersion = 1.1

5% C-thick (14 reflection+4 sources N

H>1.5 1024 cm-2)

density ~ 200 +- 50 deg-2

in agr w XRB model byGilli, Comastri, Hasinger (2006)

NH distribution vs Optical Type

Whole sample (321)Cthick candidates (14)

Consistent with evolutionary sequence:pre-QSO phaseC-thin absorbed QSO (QSOII @ high z)unobscured QSO activityquiescent spheroidal galaxyAlexander et al. 2005; Stevens et al. 2005

Model: Granato et al. 2005

Part of the missing XRB is fromintermediate z strongly absorbedmoderate luminosity, possibly C-thick sources, in a secondary, relatively low-z phase of accretion(see “downsizing” or anti-hierarchical behaviour)

Whole sample (321)QSOII (44)

Missing XRB: NH=4.5 1023 cm-2 @ z=0.8

~50% not resolved yet for E> 5 keV(Worsley et al. 2004, 2005)

The unresolved fraction increases with the energy band

Compute the contribution of the absorbed sources to the XRB

NH > 1022 cm-2

NH > 1023 cm-2

Worsley et al. 2004This work

After computing the skycoverage according to the spectral shape of each source

CONCLUSIONSDetailed X-ray Spectral Analysis of faint X-ray sources:

Towards an universal distribution of intrinsic absorption (selection effects can be easily modelled in X-rays)

>~80% of the AGNs agree with simple unification models (TypeI/TypeII Unobscured/Obscured corr.)

Evidence for strongly absorbed, C-thick sources @ z~1, and a substantial QSOII population at z>~2

Part of the missing XRB is already observed in agreement with most recent XRB synthesis models

C-thick candidates in IRAC/MIPS colors

Use secure spectral identifications in CDFS and CDFN

Norman et al. 2004

29 galaxies with good spectra in the CDFS and emission line ratios consistent with starbursts or normal galaxies give the X-ray priors. A Bayesian approach allows us to identify 74 galaxies in the CDFS and 136 in the CDFN (2 Ms)

SFR densities

Compilation from Tresse et al. 2002:

Gallego et al. 1995 (H )

Gronwall 1999

Hopkins et al. 2000

Pascual et al. 2001

Tresse et al. 2002

Sullivan et al. 2000

Lilly et al. 1996

Lines from 60 m

Saunders et al. 1990, Takeuchi et al. 2003

Norman et al. 2004

XLF consistent with a PLE ~ (1+z)2.7

Consistent with an evolution of SFR (1+z)2.7 for 0<z<1.

XLF of Star Forming Galaxies is a goal for future X-ray missions (Con-X, XEUS)

Daddi et al. 2004

K20 survey

IR selected galaxies at z~2 with massive SF

Daddi et al. 2004

Stacked image of 23 BzK galaxies; HR< -0.5 @ 2sigma ; L2-10

~1042 erg/secSFR ~ 170 M⊙ yr-1 (4 higher than LBG). SFRD of 0.04 M⊙ /yr/Mpc3

We are witnessing the massive spheroid formation epoch(the peak of just the low-z tail?)

Soft Hard

The evolution of the obscured fraction with redshift

This work

Ueda et al. 2003

Average NH artificially increases towards high-z

Tozzi, Gili, Mainieri et al. 2006

NH ~ 1020cm-2

150 and 80 net counts

Ueda et al 2003Hasinger et al. 2005

Luminosity dependent density evolution:downsizing or anti-hierarchical behaviour

ExtendedCDFS

PI N. Brandt~1000 sources(Lehmer et al. 2005)

1Ms+

4 X 240 ks

AGN Contribution to the hard XRB

CDFS (1Ms): XRB(S> 4.5×10 -16) = (1.70±0.15)×10 -11 erg s -1cm -2deg -2

90% resolved in 0.5-2 keV93% resolved in 2-8 keVAGN contribution83% in 0.5-2 keV95% in 2-8 keV(Bauer et al. 2004)

CDFN (2Ms): XRB(S> 2 ×10 -16) = (2.07±0.15)×10 -11 erg s -1cm -2deg -2

Worsley et al. 2004; 2005Missing XRB: NH=4.5 1023 cm-2 @ z=0.8

~50% not resolved yet for E> 5 keV(Worsley et al. 2004, 2005)

The unresolved fraction increases with the energy band

Compute the contribution of the absorbed sources to the XRB

Worsley et al. 2004This work

After computing the skycoverage according to the spectral shape of each source