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The Cosmic X-ray Background Facts: a Nobel prize Fictions: The AGN synthesis models (?)

The Cosmic X-ray Background Facts: a Nobel prize Fictions: The AGN synthesis models (?). Andrea Comastri (INAF- Oss. Astr. Bologna). Extragalactic Background Light. The XRB spectrum: data. (courtesy of R. Gilli). The 2-10 keV XRB intensity. (courtesy of R. Gilli). Vecchi et al. (1999).

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The Cosmic X-ray Background Facts: a Nobel prize Fictions: The AGN synthesis models (?)

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  1. The Cosmic X-ray Background Facts: a Nobel prizeFictions: The AGN synthesis models (?) Andrea Comastri (INAF- Oss. Astr. Bologna) GH2003 Workshop

  2. Extragalactic Background Light GH2003 Workshop

  3. The XRB spectrum: data (courtesy of R. Gilli) GH2003 Workshop

  4. The 2-10 keV XRB intensity (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 GH2003 Workshop

  5. 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 GH2003 Workshop

  6. XRB model formulae XRB spectrum Source spectrum X ray luminosity function (XLF) Source counts GH2003 Workshop

  7. Fit to the XRB spectrum GH2003 Workshop

  8. SOURCE COUNTS GH2003 Workshop

  9. 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 GH2003 Workshop

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

  11. Main model assumptions • The X-ray Luminosity Function and evolution of obscured AGN isunknown  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) GH2003 Workshop

  12. 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) GH2003 Workshop

  13. 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 GH2003 Workshop

  14. Hard counts (with/without Type 2 QSO) GH2003 Workshop

  15. Hard Counts (Compton thick dominated) GH2003 Workshop

  16. The deepest X-ray sky CDFS HDFN GH2003 Workshop

  17. The Deep X-ray Surveys Survey X-ray observations Sensitivity/1e-16 N. Sources Reference soft / hard CDFS1Msec 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)] GH2003 Workshop

  18. Problems • Redshift distribution • Absorption distribution • Quasar 2 GH2003 Workshop

  19. Redshift distribution in the Deep Surveys CDFS + HDFN (Hasinger et al. 2003) GH2003 Workshop

  20. 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 GH2003 Workshop

  21. Abs/unabs ratio as a function of z CDFN CDFS+CDFN CDFS GH2003 Workshop

  22. Luminosity function: • Cowie et al. 2003 • astro-ph/0301231 • Hasinger 2003 • astro-ph/0302574 GH2003 Workshop

  23. Space density: • Cowie et al. 2003: • rho_BH ~ 2x105 • Hasinger 2003 GH2003 Workshop

  24. 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 GH2003 Workshop

  25. 317 sources (Hellas2XMM + Lockman + CDFN + SSA13 -15 < logFx < -13.3 , 70% identified) GH2003 Workshop Fiore et al. 2003 astro-ph/0306556

  26. Redshift distribution (Opt +stat. ids) GH2003 Workshop

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

  28. Average spectrum Tozzi et al. 2001 GH2003 Workshop

  29. 2a) Absorption distributions2-10 keV Chandra CDFN XMM Hellas2Xmm HEAO-1 Piccinotti et al. ASCA Della Ceca et al. XMM Piconcelli et al. XMM Mainieri et al. GH2003 Workshop

  30. 2b) Absorption distribution5-10 keV NH>1022 NH>1023 open: BeppoSAX HELLAS filled: ASCA Sheep GH2003 Workshop

  31. QSO2s Absorption vs luminosity CDFS XMM Lockman Hole From Mainieri et al. (2002) GH2003 Workshop

  32. 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) GH2003 Workshop

  33. CDFS 202: QSO-2 detected 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 GH2003 Workshop

  34. 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 ? GH2003 Workshop

  35. Conclusions ? • Forget the unification scheme ? • Why the bull stop to moo at high luminosity ? • Space density and evolution of obscured sources ? • High energy spectrum ? GH2003 Workshop

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