Obscured Supermassive Black Holes

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(Obscured) Supermassive Black Holes
The Space Density of CT AGN and the XRB

• Ezequiel Treister (IfA)
• Meg Urry, Shanil Virani, Priya Natarajan (Yale)

Credit ESO/NASA, the AVO project and Paolo
Padovani
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Supermassive Black Holes
Many obscured by gas and dust

• How do we know that?
• Local AGN Unification
• Explain Extragalactic X-ray Background

Credit ESO/NASA, the AVO project and Paolo
Padovani
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Compton Thick AGN

• Defined as obscured sources with NHgt1024 cm-2.
• Very hard to find (even in X-rays).
• Observed locally and needed to explain the X-ray
  background.
• Number density highly uncertain.
• High energy (Egt10 keV) observations are required
  to find them.

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Swift
INTEGRAL
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ISDC
Swift Sources
Tueller et al. 2007
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Deep INTEGRAL Survey (3 Msec)
Significance Image, 20-50 keV
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Log N-Log S
Treister et al. in prep.
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Log N-Log S
Treister et al. in prep.
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Fraction of CT AGN
X-ray background does not constrain density of CT
AGN
Treister et al. in prep.
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CT AGN and the XRB
Treister et al. in prep.
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X-Ray Background Synthesis
Treister et al. in prep.
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Contribution of CT AGN to the XRB
Treister et al. in prep.
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CT AGN at High Redshift
Treister et al. in prep.
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How Many CT AGN?

• At low redshift (zlt0.05), 5-10 CT AGN from HEAO,
  BeppoSAX, INTEGRAL, Swift, etc.
• At high redshift, candidates from X-ray and
  mid-IR selections.
• Nothing at intermediate redshifts (z0.5-1), when
  most of the XRB is emitted until EXIST, NuSTAR
  and Simbol-X.

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CT AGN Space Density (Lxgt1045)
Polletta06
Treister et al. in prep.
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CT AGN Space Density (Lxgt1045)
Polletta06
Treister et al. in prep.
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CT AGN Space Density (Lxgt1044)
Alexander08
Tozzi06
Treister et al. in prep.
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CT AGN Space Density (Lxgt1044)
Alexander08
Tozzi06
Treister et al. in prep.
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CT AGN Space Density (Lxgt1043)
Fiore08
Tozzi06
Risaliti99
INTEGRAL
Treister et al. in prep.
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CT AGN Space Density (Lxgt1043)
Fiore08
Tozzi06
Risaliti99
INTEGRAL
Treister et al. in prep.
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CT AGN Space Density (Lxgt1042)
Daddi07
Treister et al. in prep.
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CT AGN Space Density (Lxgt1042)
Daddi07
Treister et al. in prep.
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SMBHs Spatial Density
Natarajan Treister, 2008
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UMBHs Spatial Density
Natarajan Treister, 2008
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UMBHs Spatial Density

• Self-Regulation
• Momentum-driven winds (Murray et al. 2004).
• Radiation pressure (Haehnelt et al. 98)
• Energy Driven Superwind (King 05)

Natarajan Treister, 2008
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Summary

• The number of CT AGN in the local Universe can be
  constrained, thanks to Swift and INTEGRAL.
• Number of CT AGN still roughly consistent with
  XRB, but can be increased by 4x.
• Strong decrease in the number of UMBHs -gt Self
  regulation process. (???)

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Observed X-ray Background
Frontera et al. (2006)
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AGN in X-rays
Photoelectric absorption affect mostly low energy
emission making the observed spectrum look
harder.
Increasing NH
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How to find high-z CT AGN NOW?
X-rays?
Trace rest-frame higher energies at higher
redshifts ? Less affected by obscuration
Tozzi et al. claimed to have found 14 CT AGN
(reflection dominated) candidates in the CDFS.
Polletta et al. (2006) report 5 CT QSOs
(transmission dominated) in the SWIRE survey.
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Extremely Red X-ray Objects (ERXOs)

• ERXOs are new class of X-ray emitters about which
  little is known
• 7 found in CDFS (Koekemoer et al, 2004)
• Defined by very red colors R-K gt 7 (Vega)
• Given X-ray detection and very red optical-IR
  spectrum, either
• very high redshift AGN z gt 6
• very obscured AGN with old or dusty host galaxies
  at z2-3
• Probably a heterogeneous population?

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ERXOs Examples in the ECDF-S
Urry et al. in prep.
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ECDF-S K band vs Hard X-ray Flux
ERXOs
Urry et al. in prep.
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Confirming the ERXOs Nature

• No GALEX or GEMS counterparts
• NIR spectroscopy crucial to determine the
  intrinsic nature
• ? no ERXO has a measured spectroscopic redshift
• 4 ERXOs in ECDFS are bright enough to perform NIR
  spectroscopy.
• Targeted with VLT/SINFONI IFU. Three sources
  observed.

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Sinfoni Spectroscopy
Lx 4.1x1044 erg/s ? 1.20.4
Lx 2.6x1043 erg/s ? 1.50.4
Lx 1.2x1043 erg/s ? 1.31.0
Urry et al. in prep.
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How to find high-z CT AGN NOW?
Mid-IR?
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NuSTAR