1. 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

2. 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

3. The deepest X-ray sky HDFN (Brandt et al. 2001) CDFS (Giacconi et al. 2002) Chandra Surveys, 1 Ms exposures

4. The origin of the cosmic XRB A 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) OBSCURED AGN

6. SMBH mass density from XRB (Fabian & Iwasawa 1999)

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

9. DEEP FIELDS: Redshift Distributions CDFS, Gilli 2003 CDFN, Barger et al. 2002

10. Cosmic Sheets Z=0.67 CDFS CDFN

11. X-ray source clustering Yang et al. 2003 (astro-ph/0302137) Hard X-ray sources more clustered than soft ones

12. Gilli et al. 2003 (astro-ph/0304177) The same LSS is traced by both X-ray and near IR surveys

13. Luminosity function: Cowie et al. 2003 astro-ph/0301231 Hasinger 2003 astro-ph/0302574

14. Space density: Cowie et al. 2003: rho_BH ~ 2x10 5 Hasinger 2003

15. 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

16. The Hellas2XMM survey Wide and shallow: 3 deg 2 (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)

17. X/O -------- f X /f opt > 10 Likely to be highly obscured Undetected in the R-band at R=24-25 (shallow), even R>27-28 (deep) Constant fraction over a large range of fluxes Shallow surveys pick-up brightest sources  optical identification is possible

18. Redshift from X-ray lines in the CDFN - R ~ 24 z= 1.15+-0.05

19. 317 sources (Hellas2XMM + Lockman + CDFN + SSA13 -15 < logFx < -13.3, 70% identified) Fiore et al. 2003

20. Redshift distribution (Opt +stat. ids)

21. The evolution of number and luminosity densities (Fiore et al. 2003) rho_BH ~ 4-6x10 5

22. K-band observations of 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

23. 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 ————————— Extremely red colors up to R-K~7 ! ————————— Extended morphologies Only two objects are compact (high z AGN ?) (Mignoli et al, in prep.) Pointlike, K=17.7, R-K>6.8 Elliptical, K=17.9, R-K=6.5 Cluster CD ?, K=18.7, R-K=6.0 Disky, K=18.4, R-K=5.8

24. 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

25. The X/O ratio is correlated with the R-K color: hope to get spectroscopic redshifts in the infrared

26. Evidences of interacting SMBH

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

28. Concluding Remarks The XRB appears to be dominated by low-z low-L objects The 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

29. Broad Iron Lines at high z ?

30. Comastri, Civano & Brusa (in prep.)