The Space Density of The Space Density of Compton Thick AGNCompton Thick AGN

Erin Bonning (Yale)On behalf of Ezequiel Treister

(ESO) Meg Urry (Yale)

Shanil Virani (Yale)

Compton Thick AGNCompton Thick AGN

Defined as obscured sources with NH>1024 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 (E>10 keV)

observations are required to find them.

INTEGRAL SurveyINTEGRAL Survey

• 2 Msec (expected 3 Msec by summer 2008) Deepest extragalactic INTEGRAL survey

• XMM-LSS field• Flux limit: ~4x10-12 ergs cm-2 s-1 (20-40 keV)• Area: ~1,000 deg2

• 10 Sources, ~2 Compton thick AGN

INTEGRAL Mosaic (2.2 Ms)INTEGRAL Mosaic (2.2 Ms)

Significance Image, 20-50 keVSignificance Image, 20-50 keV

MCG-02-08-014MCG-02-08-014

Maximum depth: 2.2 Ms (inner contour)

Exposure MapExposure Map

INTEGRAL Flux Limit vs. Exposure Time

Flim t–1/2

Space Density of CT AGNSpace Density of CT AGN

X-ray background does not constrain density of CT AGN

CT AGN and the XRBCT AGN and the XRB XRB IntensityHEAO-1 OriginalHEAO-1 +10%HEAO-1 +40%

Treister & Urry, 2005

Gilli et al. 2007

CT AGN and the XRBCT AGN and the XRB XRB IntensityHEAO-1 OriginalHEAO-1 +10%HEAO-1 +40%

Treister & Urry, 2005

CT AGN Space Density

Most likely solution

Gilli et al. 2007

X-ray Background X-ray Background SynthesisSynthesis

INTEGRAL AGN logN-logSINTEGRAL AGN logN-logS

Beckmann et al. 2006

(Near) Future AGN logN-(Near) Future AGN logN-logSlogS

SummarySummary

• INTEGRAL (& Swift) give important constraints on Compton Thick AGN (at z=0)

• X-ray “background” synthesis OK– (but XRBG spectrum somewhat

uncertain)• Reflection component normalization ~ 1

– (agrees with spectra)• Deeper surveys probe evolution to z~1

INTEGRAL Mosaic (2.2 Ms)INTEGRAL Mosaic (2.2 Ms)

Significance Image, 20-50 keVSignificance Image, 20-50 keV