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Boston, November 2006 Extragalactic X-ray surveys
Spectral analysis of X-ray sources in the CDFS
Paolo Tozzi
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0.3-1 keV 1-3 keV 3-7 keV
Detailed spectral analysis of X-ray
sources Tozzi, Gilli, Mainieri et al. 2006, AA,
451, 457
Rosati et al. 2002 National Geographic, Dec 2002
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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
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Compton thick candidates
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NH vs redshifts for the whole sample
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Detected fraction as a function of NH and z
z lt 0.7 0.7 lt z lt1.5 z gt 1.5
Sampling different luminosity and spectral
population at different z Selection effects are
relatively easy to model in the X-ray band
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NH histogram corrected for completeness
Corrected for completeness and sources outside
the detectability region ltlog(NH)gt
23.1 dispersion 1.1 5 C-thick (14
reflection 4 sources NHgt1.5 1024 cm-2) density
200 - 50 deg-2 in agr w XRB model by Gilli,
Comastri, Hasinger (2006)
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NH distribution vs Optical Type
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Whole sample (321) QSOII (44)
Whole sample (321) Cthick candidates (14)
Consistent with evolutionary sequence pre-QSO
phase C-thin absorbed QSO (QSOII _at_ high
z) unobscured QSO activity quiescent spheroidal
galaxy Alexander et al. 2005 Stevens et al.
2005 Model Granato et al. 2005
Part of the missing XRB is from intermediate z
strongly absorbed moderate luminosity, possibly
C-thick sources, in a secondary, relatively
low-z phase of accretion (see downsizing or
anti- hierarchical behaviour)
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The unresolved fraction increases with the
energy band
50 not resolved yet for Egt 5 keV (Worsley et
al. 2004, 2005)
Missing XRB NH4.5 1023 cm-2 _at_ z0.8
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Compute the contribution of the absorbed sources
to the XRB
NH gt 1022 cm-2 NH gt 1023 cm-2
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Worsley et al. 2004 This work
After computing the skycoverage according to the
spectral shape of each source
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CONCLUSIONS

• Detailed 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)
• gt80 of the AGNs agree with simple unification
  models (TypeI/TypeII Unobscured/Obscured corr.)
• Evidence for strongly absorbed, C-thick sources _at_
  z1, and a substantial QSOII population at zgt2
• Part of the missing XRB is already observed in
  agreement with most recent XRB synthesis models

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C-thick candidates in IRAC/MIPS colors
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Use secure spectral identifications in CDFS and
CDFN
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)
Norman et al. 2004
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SFR densities
XLF consistent with a PLE (1z)2.7 Consistent
with an evolution of SFR ? (1z)2.7 for 0ltzlt1.
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 of Star Forming Galaxies is a goal for
future X-ray missions (Con-X, XEUS)
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K20 survey
Daddi et al. 2004
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IR selected galaxies at z2 with massive SF
Soft
Hard
Stacked image of 23 BzK galaxies HRlt -0.5 _at_
2sigma L2-101042 erg/sec SFR 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?)
Daddi et al. 2004
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The evolution of the obscured fraction with
redshift
This work Ueda et al. 2003
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Average NH artificially increases towards high-z
NH 1020cm-2 150 and 80 net counts
Tozzi, Gili, Mainieri et al. 2006
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Luminosity dependent density evolution downsizing
or anti-hierarchical behaviour
Ueda et al 2003 Hasinger et al. 2005
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Extended CDFS PI N. Brandt 1000 sources (Lehmer
et al. 2005) 1Ms 4 X 240 ks
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AGN Contribution to the hard XRB
90 resolved in 0.5-2 keV 93 resolved in 2-8
keV AGN contribution 83 in 0.5-2 keV 95 in 2-8
keV (Bauer et al. 2004)
CDFS (1Ms) XRB(Sgt 4.510 -16) (1.700.15)10
-11 erg s -1cm -2deg -2
CDFN (2Ms) XRB(Sgt 2 10 -16) (2.070.15)10
-11 erg s -1cm -2deg -2
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The unresolved fraction increases with the
energy band
50 not resolved yet for Egt 5 keV (Worsley et
al. 2004, 2005)
Missing XRB NH4.5 1023 cm-2 _at_ z0.8
Worsley et al. 2004 2005
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Compute the contribution of the absorbed sources
to the XRB
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Worsley et al. 2004 This work
After computing the skycoverage according to the
spectral shape of each source