Andrea Comastri (INAF- Oss. Astr. Bologna) The Cosmic X-ray Background Facts: a Nobel prize Fictions: The AGN synthesis models (?) Andrea Comastri (INAF- Oss. Astr. Bologna) sabato 17 novembre 2018 GH2003 Workshop

Extragalactic Background Light sabato 17 novembre 2018 GH2003 Workshop

The XRB spectrum: data (courtesy of R. Gilli) sabato 17 novembre 2018 GH2003 Workshop

The 2-10 keV XRB intensity Vecchi et al. (1999) Lumb et al. (2002) (courtesy of R. Gilli) Vecchi et al. (1999) Lumb et al. (2002) Kushino et al. (2002) Tozzi et al. (2001) Integrated flux from resolved sources sabato 17 novembre 2018 GH2003 Workshop

The origin of the cosmic XRB Diffuse gas can contribute significantly to the cosmic XRB only below 2 keV (CMB argument, Wright et al. 1994; <10% Rosati et al. 2002)  the hard XRB is due to single sources OBSCURED AGN Modificare o togliere sabato 17 novembre 2018 GH2003 Workshop

XRB model formulae XRB spectrum Source spectrum X ray luminosity function (XLF) Source counts sabato 17 novembre 2018 GH2003 Workshop

Fit to the XRB spectrum sabato 17 novembre 2018 GH2003 Workshop

SOURCE COUNTS sabato 17 novembre 2018 GH2003 Workshop

Some “Facts” 60-70% of the XRB is made by sources around the knee of source counts (logfx=-14+-1) The 2-10 keV spectrum is a flat power law (0.4  HEAO1-ASCA-BeppoSAX-XMM,…) Absorption distribution logNH=21-24 Luminosity distribution logLx = 44+-1.5 sabato 17 novembre 2018 GH2003 Workshop

Several “Fictions” Compton thick (log NH > 24) sources Optical continuum and emission line properties of hard X-ray sources Host galaxy properties sabato 17 novembre 2018 GH2003 Workshop

Main model assumptions The X-ray Luminosity Function and evolution of obscured AGN is unknown  TypeII=TypeI The absorption distribution of obscured AGN is unknown (but the nearby Universe)  XRB fit Simple SED (power law + absorption log NH = 21-25) sabato 17 novembre 2018 GH2003 Workshop

Observational constraints: N(NH), N(z) Risaliti et al. (1999) Observed in Seyfert 2s Comastri et al. (1995) Fitted to the XRB spectrum Sy2/Sy1 ratio at z=0: 3-5 (Maiolino & Rieke 1995) sabato 17 novembre 2018 GH2003 Workshop

Observational constraints: need for QSO2 High Luminosity (logL(X)> 44) highly absorbed (log(NH)=23+/-1) sources are required to fit bright counts Compton Thick QSO (logNH>24) are not energetically important sabato 17 novembre 2018 GH2003 Workshop

Hard counts (with/without Type 2 QSO) sabato 17 novembre 2018 GH2003 Workshop

Hard Counts (Compton thick dominated) sabato 17 novembre 2018 GH2003 Workshop

The deepest X-ray sky HDFN CDFS sabato 17 novembre 2018 GH2003 Workshop

The Deep X-ray Surveys Survey X-ray observations Sensitivity/1e-16 N. Sources Reference soft / hard CDFS 1Msec Chandra ACIS-I 0.5 / 4 * 346 Giacconi et al.(2002) 500 ksec XMM CDFN 2 Msec Chandra ACIS-I 0.2 / 1 503 Alexander et al. (2003) 230 ksec XMM Lockman 100 ksec XMM 3.0 / 14 ~200 Hasinger et al. (2001) 300 ksec Chandra HRC 1.5 Msec ROSAT 260 ksec ASCA Lynx 180 ksec Chandra 1.7 / 15 153 Stern et al. (2002) 300 ksec XMM SSA13 100 ksec Chandra 2.3 / 25 40 Mushotzky et al. (2000) * extended to 0.2 / 2 by Campana et al. (2001) [see also Moretti et al. (2002)] sabato 17 novembre 2018 GH2003 Workshop

Problems Redshift distribution Absorption distribution Quasar 2 sabato 17 novembre 2018 GH2003 Workshop

Redshift distribution in the Deep Surveys CDFS + HDFN (Hasinger et al. 2003) sabato 17 novembre 2018 GH2003 Workshop

Gandhi & Fabian 2003 Franceschini et al. 2002– link with IR? Best fit to the peak, deficit at z>1 most likely due to spectroscopic incompleteness… BUT sabato 17 novembre 2018 GH2003 Workshop

Abs/unabs ratio as a function of z CDFN CDFS+CDFN CDFS sabato 17 novembre 2018 GH2003 Workshop

Luminosity function: Cowie et al. 2003 Hasinger 2003 astro-ph/0301231 sabato 17 novembre 2018 GH2003 Workshop

Space density: Hasinger 2003 Cowie et al. 2003: rho_BH ~ 2x105 sabato 17 novembre 2018 GH2003 Workshop

X/O -------- fX/fopt > 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 sabato 17 novembre 2018 GH2003 Workshop

317 sources (Hellas2XMM + Lockman + CDFN + SSA13 -15 < logFx < -13.3 , 70% identified) sabato 17 novembre 2018 GH2003 Workshop Fiore et al. 2003 astro-ph/0306556

Redshift distribution (Opt +stat. ids) sabato 17 novembre 2018 GH2003 Workshop

The evolution of number and luminosity densities (Fiore et al The evolution of number and luminosity densities (Fiore et al. 2003, astro-ph/030556) sabato 17 novembre 2018 GH2003 Workshop rho_BH ~ 4-6x105

Average spectrum Tozzi et al. 2001 sabato 17 novembre 2018 GH2003 Workshop

2a) Absorption distributions 2-10 keV Chandra CDFN XMM Hellas2Xmm HEAO-1 Piccinotti et al. ASCA Della Ceca et al. XMM Piconcelli et al. XMM Mainieri et al. sabato 17 novembre 2018 GH2003 Workshop

2b) Absorption distribution 5-10 keV NH>1022 NH>1023 open: BeppoSAX HELLAS filled: ASCA Sheep sabato 17 novembre 2018 GH2003 Workshop

Absorption vs luminosity CDFS XMM Lockman Hole QSO2s From Mainieri et al. (2002) sabato 17 novembre 2018 GH2003 Workshop

3) Can we survive without QSO2 ? QSO2 (luminous obscured sources) do exist…, but they are NOT luminous Seyfert 2. EROs, high fx/fopt sources , broad lines quasars, ULIRGs… X-ray and optical properties do not go hand in hand Are they enough ? (see discussion) sabato 17 novembre 2018 GH2003 Workshop

CDFS 202: QSO-2 detected Norman et al. 2002 LX ~ 1045 erg/s NH ~ 1024cm-2 narrow high-excitation lines Fe-line @ 6.4 keV VLT-spectrum Chandra spectrum 1.4 keV = 6.4/(1+z) Norman et al. 2002 sabato 17 novembre 2018 GH2003 Workshop

N(Z) predicted to peak around 1.5-2 Now it seems to peak at 0.7-1 Change the XLF parameters rather than assuming extremely fast evolution N(NH)  HR vs. real spectra N(NH)  lack of obscured sources at bright fluxes (30% obs vs. 50% expect) Dependence of NH vs. z and/or luminosity ? N(NH)+sharp drop of <alpha>  things are rapidly changing around logfx=-14 ? sabato 17 novembre 2018 GH2003 Workshop

Conclusions ? Forget the unification scheme ? Why the bull stop to moo at high luminosity ? Space density and evolution of obscured sources ? High energy spectrum ? sabato 17 novembre 2018 GH2003 Workshop