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.)