Revealing the heavily obscured agn population with radio selection
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Revealing the heavily obscured AGN population with radio selection. Aim: to find ALL the AGN. Wilkes, Kuraszkiewicz , Atanas , Haas, Barthel , Willner , Leipski , Worrall Birkinshaw , Antonucci,Ogle , U.T. Cobley & all. Powerful, FRII Radio Galaxies.

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Revealing the heavily obscured agn population with radio selection

Revealing the heavily obscured AGN population with radio selection

Aim: to find ALL the AGN

Wilkes, Kuraszkiewicz, Atanas,

Haas, Barthel, Willner, Leipski, Worrall Birkinshaw, Antonucci,Ogle,

U.T. Cobley& all

HEAD Meeting


Powerful frii radio galaxies
Powerful, FRII Radio Galaxies selection

  • 3CRR, z~1-2, low-frequency radio-selected

  • High L/LEdd, log L~1045-46 ergs-1

  • Orientation is dominant variable

Cygnus A

HEAD Meeting


Chandra x ray luminosities for nl bl agn
Chandra selection X-ray Luminosities for NL+BL AGN

Log Hard X-ray Luminosity

Log Radio Luminosity (5GHz)

  • Radio (=AGN) Power comparable

  • X-ray (“observed”) luminosity of NL sources 10-1000* lower

HEAD Meeting


X ray hardness ratio
X-ray Hardness Ratio selection


z~0.5-1, 3CRRs


  • Simple Unification:

    • QSO – face-on: bright + soft (Γ~1.9)

    • NLRG – edge-on: faint + hard

  • Exceptions:

    • 2 QSOs + 1 NLRG: intermediate

    • 5 soft NLRG



X-ray Hardness Ratio

HEAD Meeting


X ray luminosity is obscured

Compton Thick selection

X-ray Luminosity is obscured

  • HR hardens as LX decreases

  • Weakest sources include 2ndcomponent: soft excess

  • Possibilities:

    • Scattered nuclear light

    • Extended emission (NLR?) (Wang et al.)

    • Jet-related (Hardcastle et al.)

  • Obscuration → decrease Lx

  • Hard to find + measure obscured sources

  • HR ≠> NH for low LX

Intermediate QSOs



HEAD Meeting


Compton thick l oiii l x
Compton Thick? : L selection[OIII]/LX

  • 4 soft + 5 hard NLRGs:

    • high L([OIII]λ5007)/LX

  • → 9 Compton Thick (CT) candidates

  • X-ray absorption:

    • HR → NH~1020-23cm-2

    • L[OIII]/LX→ NH>1024.5cm-2

  • LX/LR → NHestimate for low S/N sources

Juneau et al. 2011

Edge-on Radio Core Fraction Face-on

HEAD Meeting


X ray absorption vs radio core fraction

Radio Core Fraction selection

X-ray Absorption vs. Radio Core-Fraction

  • Strongly correlated

  • → Observed X-rays are consistent with orientation dependent obscuration of Unified Models



HEAD Meeting


N h distribution
N selectionH Distribution

  • NLRG NH peaks at high values, >1024cm-2

  • Consistent with z<1 3CRRs

    (Hardcastle et al 2009)

  • Obscured fraction ~ 0.5 higher than typical 0.1-0.3 for high Luminosity AGN

  • CT fraction ~ 0.2

  • Consistent with CXRB models (Gilli et al. 2007)

HEAD Meeting


Conclusions selection

  • Orientation alone → range of *1000 in observed LX

  • High S/N X-ray spectra required to accurately estimate intrinsic NHand LX → both generally underestimated

  • Underestimation of intrinsic LX leads to:

    • High LXAGN: unobscured, #s underestimated

    • Low LX AGN: obscured, #s overestimated

    • Thus:

      • Luminosity Functions } increase towards lower LX

      • Obscured fractions }

HEAD Meeting


Luminosity function and obscured fraction
Luminosity Function and obscured fraction selection

Mayo & Lawrence 2013

50% covered

Change in LF if all are CT

Obscured fraction vs LX

HEAD Meeting


Conclusions selection

  • Luminosity Functions may be flatter, high luminosity active galaxies more numerous than currently deduced

  • A luminosity-dependent obscured fraction may not be required to explain X-ray and optical data

    Take care when estimating obscuration for sources in X-ray samples

HEAD Meeting