The evolution of SMBH from Hard X-ray surveys

Andrea Comastri (INAF – Osservatorio di Bologna – Italy)

•The XRB as a tracer of SMBH mass density•Hard X-ray surveys: observational results•Near-IR observations of hard X-ray sources•Evidences of merging•Conclusions and perspectives

Hard X-ray Surveys

Most direct probe of the super-massive black hole (SMBH) accretion activity recorded in the XRB spectral energy density

Chandra and XMM surveys: SMBH census is almost complete (integral) obscured AGN make the bulk of the XRB

The light-up and evolution of obscured accreting SMBH is still largely unknown

(differential) XLF evolution of obscured AGN

The deepest X-ray sky

HDFN (Brandt et al. 2001) CDFS (Giacconi et al. 2002)

Chandra Surveys, 1 Ms exposures

The origin of the cosmic XRBA truly diffuse component not exceeding 10% of

the observed flux (warm IGM, missing baryons …) may still be present in the soft (below 2 keV) X-ray band

the hard XRB (2-100 keV) is due to single sources (X-ray surveys, CMB argument)

OBSCUREDAGN

SMBH mass density from XRB (Fabian & Iwasawa 1999)

Where all the SMBH have gone ? N(L), N(z), efficiency, bolometric correction ?

DEEP FIELDS: Redshift Distributions

•CDFS, Gilli 2003•CDFN, Barger et al. 2002

Cosmic Sheets

Z=0.67

•CDFS •CDFN

X-ray source clusteringYang et al. 2003 (astro-ph/0302137)

•Hard X-raysources more clustered thansoft ones

•Gilli et al. 2003 (astro-ph/0304177)

The same LSS is traced by both X-ray and near IRsurveys

Luminosity function:

•Cowie et al. 2003astro-ph/0301231

•Hasinger 2003astro-ph/0302574

Space density:

•Cowie et al. 2003: rho_BH ~ 2x105

•Hasinger 2003

Deep Chandra surveys: limits

Small solid angle lack of high z high L objects

Soft X-ray response biased against highly obscured objects

Limited by faint optical counterparts and thus incomplete at high-z

The Hellas2XMM survey Wide and shallow: 3 deg2 (15 XMM public fields)

~30 sources/field, Fx>10-14

Bulk of the XRB Rare and peculiar sources, avoid cosmic variance

Relatively “easy” multi-wavelength follow-up (ESO-VLT,3.6m, ATCA, VLA, TNG & Chandra)

X/O--------fX/fopt > 10Likely to be highly obscured

Undetected in the R-band at R=24-25 (shallow), even R>27-28 (deep)

Constant fractionover a large rangeof fluxes

Shallow surveys pick-up brightest sources optical identification is possible

Redshift from X-ray linesin the CDFN - R ~ 24 z= 1.15+-0.05

317 sources (Hellas2XMM + Lockman + CDFN + SSA13 -15 < logFx < -13.3 , 70% identified) Fiore et al. 2003

Redshift distribution (Opt +stat. ids)

The evolution of number and luminosity densities (Fiore et al. 2003)

• rho_BH ~ 4-6x105

K-band observationsof high X/0

Selection:•11 sources •R > 24.5•Flx(2-10) > 1.2 10-14

•VLT/ISAAC•1 hour exp. in K•Seeing < 0.7 arcsec•Mag lim. ≈ 21

ISAAC VLT K-band observations of high X/O

10/11 sources with a bright IR counterpart in the error box: ALL with R-

K>5

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Extremely red colors

up to R-K~7 !up to R-K~7 !

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Extended morphologies

Only two objects are

compact (high z AGN ?)

(Mignoli et al, in prep.)

Pointlike, K=17.7, R-K>6.8Elliptical, K=17.9, R-K=6.5Cluster CD ?, K=18.7, R-K=6.0Disky, K=18.4, R-K=5.8

High quality imaging

Surface brightness

and effective radius

BH mass estimate

via FP and M(BH) vs. sigma

relation•Red=de Vaucouleurs

•Blue=exponential

NEED z

The X/O ratio is correlated with the R-K color:

hope to get spectroscopic redshifts in the infrared

Evidences of interacting SMBH

Near IR imaging of hard X-ray sources:X-ray bright optically normal galaxies

Concluding Remarks The XRB appears to be dominated

by low-z low-L objectsThe SMBH mass density is almost

equally accounted for by unobscured and obscured AGN (lower mass on average)

Obscured AGN are hosted by a wide variety of galaxy types

Redshifts for optically faint (high X/O) obscured sources urgently needed

Broad Iron Lines at high z ?

Comastri, Civano & Brusa (in prep.)