1. Early accreting SMBHs: forecasts for the next decade with the Wide Field X-ray Telescope R. Gilli (INAF-OABo), P. Tozzi, P. Rosati, S. Borgani, M. Paolillo, M. Brusa, A. Comastri, F. Marulli, C. Vignali and the WFXT-team.

2. About 40 QSOs at z>5.7, ~15 at z>6, mostly from SDSS and CFHQZ. They are already “mature”: high metallicity and dust content and large, ~10 9 M sun, BH masses (Beelen+06, Juarez +09, Kurk +09) L~L edd M BH /M * larger than in the local Universe Highly biased They are luminous L>L* QSOs (logL x >44, logL bol >45.5) But SDSS and CFHQZ QSOs likely NOT representative of whole z>6 population QSOs at z>6 where do we stand Lamastra+10 Willott+09

3. Optical vs X-ray selection Spectroscopically confirmed high-z AGN to date SDSSX-rays z > 3800050 z > 4150011 z > 5 150 3 z > 6 10 0 z > 4 X-ray selection can pick up fainter (low-lum or obscured) AGN Obscured AGN more abundant than unobscured by a factor up to ~10 X-rays sample the bulk of the AGN population X-ray surveys still limited by sensitivity over solid angle Optical z>6 QSOs: 1/500 deg 2 ;1/30 deg 2

4. NEED LARGE SKY AREAS TO DEEP X-RAY SENSITIVITY!

5. The Wide-Field X-Ray Telescope (WFXT) Institutes involved: CfA, JHU/APL, MIT, MSFC, PSU, STScI INAF, ASI/ASDC, Uni. Trieste, Napoli, Bologna. ESO, U. Durham PI: Steven Murray (CfA) Senior Advisor: Riccardo Giacconi (JHU) Project Scientist: Andrew Ptak (GSFC) Basic Layout 3 mirror/CCD modules 1 deg 2 FOV 1 m 2 A eff @ 1 keV 5-10” HEW resolution constant across FOV 5 years operations launch 2016? An X-ray survey mission submitted to the Decadal Survey

6. A key feature for surveys: constant PSF HEW = 10” @ 0.1 keV Chandra Polynomial perturbation of standard design (Burrows, Burg, Giacconi 92 Conconi+10) Ghigo+99 Proven technology: need to improve on PSF

7. A eff × = grasp = etendue = survey speed GRASP @ 1.5 keV (deg 2 cm 2 ) IXO

8. WFXT simulations of the COSMOS field Chandra 21 daysXMM 18 days WFXT 3.6 hrs 1 deg 2 f lim ~3x10 -16 cgs

9. Sky coverage and survey strategy Three WFXT surveys Wide 20000 deg 2 Medium 3000 deg 2 Deep 100 deg 2 Total sample of 1.5 10 7 AGN 5 10 5 clusters 10 5 galaxies

10. How many z>6 AGN will we see with WFXT? Two possible ways to make predictions on the high-z Universe: 1)extrapolate from known XLF towards high-z and low luminosities 2) use semi-analytic models of BH/galaxy coevolution

11. decline: exponential decrease at all Lx. max. XLF: exponential decrease at high Lx, constant density at low Lx (it is the XLF that predicts the maximum number of high-z AGN while being in agreement with current data) decline Extrapolations of known XLF See Brusa+09 for decline up to z=4 at Lx>44.2

12. Semi-analytic models (SAMs) of BH/galaxy evolution The Merger Tree Marulli+09 Ansatz: nuclear trigger at merging Free parameters: - BH seeds; from 10 2 to 10 5 M sun : remnant of PopIII stars? Cloud direct collapse? - BH abundance/location: 1σ, 3σ, 5σ peaks? - Recipes for accretion  AGN lightcurves - SED (eg obscuration) - Room for accretion due to internal secular processes not related to mergers Kauffmann&Heahnelt00, Volonteri+06, Salvaterra+07, Rhook&Haehnelt08, Menci+08, Marulli+09, Lamastra+10)

13. decline Rhook Marulli Rhook Marulli decline Space densities of X-ray AGN Completely uncharted territory: predictions for high-z Universe very uncertain, even by a few orders of magnitude

14. Observations of significant samples at z>6 would constrain the physics of early BH formation disentangling between several scenarios How many WFXT will see? Wild range of predictions for high-z AGN

15. ~1600 AGN at z>6 ~70 AGN at z>8 down to L<L*, less biased AGN important also for re-ionization studies High-z AGN yield in the decline scenario

16. Synergies with multi- wide area surveys Surveys on ~1500-3000 deg 2 or more WFXT medium: 1000 AGN expected at z>6 600 unobscured, all seen as dropouts by LSST Brown dwarfs are 300 times fainter in the X-rays than AGN Any match between an optical dropout and an X-ray source will pick a high-z AGN Perfect synergy with eg. LSST

17. Final remarks ~15 millions AGN detected by WFXT WFXT will break through the high-z Universe: 1600 AGN at z>6 representative of the whole population * UNIQUE * WFXT surveys match in area and sensitivity next-generation multi-wavelength surveys (Pan-STARRS, LSST, VISTA, …) http://wfxt.pha.jhu.edu http://www.wfxt.eu