The quest for early Black Holes Andrea Comastri (INAF-Bologna) Roberto Gilli (INAF-Bologna) Cristian Vignali (Bologna University) Marcella Brusa (MPE) and many others
Outline High redshift (z > 3) AGN in present X-ray surveys The demography of the first (z > 6) (obscured ) SMBH : Overview of theoretical models The demography of the first (z > 6) SMBH : an observer approach Requirements for XEUS observations
Wall et al., 2005 Hiigh luminosity QSO High-z QSO? Radio QSO (Wall et al., 2005) Soft X-ray ROSAT/Chandra/ XMM (Hasinger, Miyaji & Schmidt 2005) Chandra/ROSAT(Silverman et al. 2004) Optical QSOs (Schmidt et al., 1995, Fan et al. (2001,2004) Very large solid angle & deep surveys required to study z>5 QSOs
SDSS space density of luminous Mi < -27.6 optically selected QSO z < 5 (Richards+06) z ~ 6 space density (Fan+01;04) Assuming a ox ~ 1.65 (Vignali+03;Steffen+06) Lx > 10 45 cgs Hasinger+05 XLF of Type1 QSO plus exp. decay Schmidt+95 (no fit)
Gilli,AC,Hasinger 07 AGN synthesis L x > 10 42 cgs With and whitout decline at high z (> 2.7 following Schmidt+95)
COSMOS z > 3 QSO Model with constant evolution at high z (GCH07) Model with exponential decline at z>2.7 (Schmidt+95) model folded with selection effects (limiting flux) model folded with selection effects (limiting flux) Brusa,AC,Gilli+08
Observed counts 0.5-2 kev COSMOS (> 10-15 cgs) CDFN-CDFS (~ 10-16 cgs) Sampling luminous Massive QSO (though less extreme than SDSS)
42-43 43-44 44-45 Menci Fiore +08
First BH According to theoretical models MBH may grow from: Direct Cloud Collapse - 10 4-10 6 M sun (Koushiappas+04)) Pop III remnants 10 2-10 3 M sun (Volonteri+03) Mass Growth has to be efficient (SMBH in place @ z~6) (massive seeds alleviate the problem) Eddington limited (lum & redshift dependent?) Rapid growth (N(z) skewed towards high z) Fraction of active BH as a function of time Unresolved XRB, X-ray counts, Mass function
Is there enough time to form Black Holes? M(t) = M(t 0 ) exp { ε L ( 1 - ε M ) / ε M * (t - t 0 ) / τ E } τ E = 0.45 Gyr ε L = L / L E ε M = L / M c 2 SuperEddington Volonteri Rees 06 The highest z QSO (z = 6.43) has a mass of ~ 10 9 M A likely candidate ε=0.1 for a seed BH is the remnant of Pop III Star with M >~ 300 M ε=0.2 The higher the efficiency (ε M ) the longer is the time needed to grow. ε=0.4 If accretion is via a thin disc the BH is efficiently spin up and ε M reach 0.3-0.4 requiring about 2 Gyrs to reach the observed mass
Volonteri+06
Salvaterra+06 Rhook Salvaterra+06 & Haenelt 08 Chandra > 10-16 0.5-2.0 kev Solar masses bins > 10-17 Chandra > 10-16
The XLF of high z (> 3) AGN Consistent (by construction) with present obs. Schechter func. α= 1 log L * = 44 Matched with Declining low -z XLF (HMS05)
Z > 6 28-54 7x7-10x10 arcmin FOV Z > 8 8-16
The number Counts of z > 4 QSO in some models are probably too generous
CONFUSION? F x ~ 10-17 cgs N(>S) ~ 20000 deg -2 F x ~ 4 x 10-18 cgs N(>S) ~ 30000 deg -2 Galaxies counts? 1/30 source per beam (no clustering) Gaussian PSF HEW 5 arcsec
CT AGN only barely sampled by deep Chandra and XMM surveys (i.e. Tozzi+06) Relative fraction is steeply increasing At 10-17 cgs the bulk of the population should be detected Z = 5 L min ~ 10 42 Z = 10 L min ~ 10 43
Deep X-ray spectroscopy F soft ~ 8 x 10-18 log L X ~ 42.5-43
Synergies HST and Spitzer discovery of a candidate z ~ 7.6 (lensed) galaxy candidate (Bradley+08) J 110 (intrinsic) ~ 27.7 AB JWST Nirspec Sensitivity AB ~ 29 in 100 ks The high - redshift Universe is a key science driver of both JWST and ALMA NirSpec ~ AB (1-5 µm) ~ 26.2 (in 10 ks)
Summary First Obscured (?) spinning (?) SMBH: Large sky area (i.e. erosita/wfxt) plus ultra-deep XMM / Chandra will surely help to sharpen the case for XEUS Low Mass BH are expected to be numerous at z > 6, SDSS detected the super-rare peaks Deep X-rays are needed to pick up the very first BH (ALMA JWST SKA E-ELT) > 5 m2 @ 1 kev + < 5 arcsec resolution