Obscured AGN and XRB models

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Obscured AGN and XRB models
Andrea Comastri (INAF-OABologna-Italy) Roberto
Gilli (INAF-OABologna-Italy) F. Fiore
(INAF-OARoma-Italy) G. Hasinger
(MPE-Garching- Germany) M. Brusa
(MPE-Garching-Germany) C. Vignali
(Bologna University) R. Della Ceca
(INAF-OABrera-Italy) G. Malaguti
(INAF-IASFBo-Italy)
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• Deep X-ray surveys have resolved some 80 of the
  XRB (below a few keV ) but only 50 gt 6 keV
  and a few (1-2) above 10 keV.
• Wealth of X-ray and multiwavelength follow-up
  available -gt possible to predict the missing
  population (Compton Thick AGN)
• The missing population may provide an important
  contribution to the BH mass function SMBH/galaxy
  evolution, accretion rates, Eddington ratios,

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Frontera07 astro-ph/0611228
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Model scheme

• XRB flux uncertain , so use the more robust
  constraints below 10 keV (eg. source counts) to
  lock the properties (eg obs/unobs ratio, NH
  dist.) of the Compton Thin (log NH lt 24) AGN
• Estimate the Compton Thin/Unobs. Ratio by
  comparing hard vs. soft XLF.
• Absorption distribution from X-ray counts.
• Include continuum slope dispersion.
• Add Compton thick AGN to fit the 30 keV bump
• Verify assumptions/make predictions on Compton
  Thick AGN

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Unabsorbed logNHlt21 (plus Compton reflection)
Compton-Thin 21ltlogNHlt24 Compton-Thick logNHgt2
4 Mildly (log NH 24-25) (NGC 6240,
Circinus) Heavily (log NH gt25) (NGC1068)
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Best fit ratios 4 at low Log Lx lt
44 Luminosities 1 at high Log Lx gt
44 luminosities
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X-ray logN-logS
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NH distribution
Thick
T h i n
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• Radio loud AGN / Blazars contribute some 10 to
  the soft XRB (Galbiati et al 2004 Giommi et al
  2006)
• Normalizing to 1 keV for a range of slopes
  (0.5-0.7) a break or cut-off must be present
  around 1 MeV otherwise the soft-gamma-ray
  background would be exceeded

High energy cut-off 100-400 keV
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Unresolved Background
AC 05
Worsley05

• hard X-ray surveys still miss the most obscured
  sources (do not sample the XRB peak)
• Missing population (numerous) moderate luminous,
  log NH gt 23, z 0.5-2
• (Worsley04,05, AC 04,05) and Compton Thick AGN
  (log NH gt 24)

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70-75 of The BeppoSAX/ INTEGRAL 10-40
keV XRB Resolved
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Obscured AGN fraction vs sample limiting flux
All abs.
Thick
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Expected number of sources per SX field Gilli
07 La Franca05 Della Ceca
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SUZAKU OBSERVATION OF Mildly CT nearby galaxies
AC07 (astro-ph/0704.1253)
Scattering fraction lt 0.5
NGC5728
Scattering fraction 2
See also Wilman et al. 2002 HyLIG
NGC4992
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4 X
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Heavily Thick will not be well sampled by
deep hard X-ray Surveys
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Local Black Holes and AGN relics

• Marconi et al. 2004 have shown that local BHs are
  relics of AGN activity by comparing
• the local BH mass function (from galaxy L/s
  functions and MBH-Lbul/MBH-se)
• the relic BHMF (from AGN luminosity function and
  continuity equation)
• Importance of AGN LF even
• the hard (2-10 keV) XLF does not sample the whole
  AGN population.
• Heavily obscured Compton-thick AGN are missing ...

Hard-X LF
Soft-X LF
Qso LF
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• Correction for Compton-Thick sources from XRB
  models ? whole
• AGN pop considered
• The only free parameters are the accretion
  efficiency and Eddington ratio
• L e dM/dt c2
• L ? LEdd

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Radiative Efficiency and Fraction of Eddington
luminosity

• Determine locus in e-? plane where there is the
  best match between local and relic BHMF!
• e0.04-0.10 ?0.08-0.5 which are consistent
  with common beliefs on AGNs

CT space density degenerates with accretion
efficiency and geometry of reflecting thick
matter
2
0.5
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• Effect of changing scattering efficiency to
  compute pure reflection spectra of Compton-Thick
  sources

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Obscured AGN and SMBH censusobservation
strategies

• A spectral survey of local CT Seyfert 2 galaxies
  previously discovered by BeppoSAX, INTEGRAL Swift
  and Suzaku. This should be accompanied by a
  volume limited survey of IR-bright or
  OIII-bright or galaxies which have not shown
  strong X-ray emission below 10 keV, to search for
  highly CT objects.
• A spectral survey of moderately obscured luminous
  QSOs discovered by XMM, Chandra up to z1 (High
  luminosity)
• Deep observations to search for faint mildly CT
  AGN serendipitous survey (high redshift)
• A survey of candidate CT AGN selected using their
  infrared emission (Spitzer/Herschel).

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Summary

• A large fraction of the 10-40 keV XRB (2/3 -
  3/4) will
• be resolved at a limiting flux of 6 x
  10-15 cgs
• A major breaktrough is foreseen (compare
  with ROSAT
• and Chandra better than ASCA and BeppoSAX)
• A large population of CT AGN (as large as
  Cthin ?) is waiting to be discovered by sensitive
  hard ( gt 10 keV) X-ray observations
• Statistically meaningful sample of the most
  obscured AGN
• over a broad range of fluxes and
  luminosities -gt XLF and evolution, SMBH assembly
  and distribution, geometry of
• obscuring/reflecting gas,