1 / 23

Obscured AGN and XRB models

Andrea Comastri (INAF-OABologna-Italy) Roberto Gilli (INAF-OABologna-Italy) F. Fiore (INAF-OARoma-Italy) G. Hasinger (MPE-Garching- Germany) M. Brusa (MPE-Garching-Germany) C. Vignali (Bologna University)

becka
Download Presentation

Obscured AGN and XRB models

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Andrea Comastri (INAF-OABologna-Italy) Roberto Gilli (INAF-OABologna-Italy) F. Fiore (INAF-OARoma-Italy) G. Hasinger (MPE-Garching- Germany) M. Brusa (MPE-Garching-Germany) C. Vignali (Bologna University) R. Della Ceca (INAF-OABrera-Italy) G. Malaguti (INAF-IASFBo-Italy) Obscured AGN and XRB models

  2. Deep X-ray surveys have resolved some 80% of the XRB (below a few keV ) but “only” 50% > 6 keV and a few (1-2%) above 10 keV. • Wealth of X-ray and multiwavelength follow-up available -> possible to predict the missing population (Compton Thick AGN) • The missing population may provide an important contribution to the BH mass function SMBH/galaxy evolution, accretion rates, Eddington ratios, … SimbolX, May 15, 2007

  3. SimbolX, May 15, 2007

  4. Frontera+07 astro-ph/0611228 SimbolX, May 15, 2007

  5. Model scheme • XRB flux “uncertain”, so use the more robust constraints below 10 keV (eg. source counts) to lock the properties (eg obs/unobs ratio, NH dist.) of the Compton Thin (log NH < 24) AGN • Estimate the Compton Thin/Unobs. Ratio by comparing hard vs. soft XLF. • Absorption distribution from X-ray counts. • Include continuum slope dispersion. • Add Compton thick AGN to fit the 30 keV bump • Verify assumptions/make predictions on Compton Thick AGN

  6. Unabsorbed: logNH<21 (plus Compton reflection) Compton-Thin: 21<logNH<24 Compton-Thick: logNH>24 Mildly (log NH =24-25) (NGC 6240, Circinus) Heavily (log NH >25) (NGC1068) SimbolX, May 15, 2007

  7. Best fit ratios ~ 4 at low Log Lx < 44 Luminosities ~ 1 at high Log Lx > 44 luminosities SimbolX, May 15, 2007

  8. X-ray logN-logS SimbolX, May 15, 2007

  9. NHdistribution Thick T h i n SimbolX, May 15, 2007

  10. Radio loud AGN / Blazars contribute some 10% to the soft XRB (Galbiati et al 2004; Giommi et al 2006) • Normalizing to 1 keV for a range of slopes (0.5-0.7) a break or cut-off must be present around 1 MeV otherwise the soft-gamma-ray background would be exceeded High energy cut-off 100-400 keV SimbolX, May 15, 2007

  11. Unresolved Background AC 05 Worsley+05 hard X-ray surveys still miss the most obscured sources (do not sample the XRB peak) Missing population: (numerous) moderate luminous, log NH > 23, z = 0.5-2 (Worsley+04,05, AC 04,05) and Compton Thick AGN (log NH > 24) SimbolX, May 15, 2007

  12. SimbolX, May 15, 2007

  13. 70-75% of The BeppoSAX/ INTEGRAL 10-40 keV XRB Resolved

  14. Obscured AGN fraction vs sample limiting flux All abs. Thick SimbolX, May 15, 2007

  15. Expected number of sources per SX field Gilli +07 La Franca+05 Della Ceca

  16. SUZAKU OBSERVATION OF Mildly CT nearby galaxies AC+07 (astro-ph/0704.1253) Scattering fraction < 0.5 % NGC5728 Scatteringfraction ~ 2% See also Wilman et al. 2002 HyLIG NGC4992 SimbolX, May 15, 2007

  17. 4 X SimbolX, May 15, 2007

  18. Heavily Thick will not be well sampled by deep hard X-ray Surveys

  19. Local Black Holes and AGN relics Hard-X LF • Marconi et al. 2004 have shown that local BHs are relics of AGN activity by comparing: • the local BH mass function (from galaxy L/σ functions and MBH-Lbul/MBH-σe) • the relic BHMF (from AGN luminosity function and continuity equation) Importance of AGN LF: even the hard (2-10 keV) XLF does not sample the whole AGN population. Heavily obscured Compton-thick AGN are missing ... Soft-X LF Qso LF SimbolX, May 15, 2007

  20. Correction for Compton-Thick sources from XRB models  whole AGN pop considered • The only free parameters are the accretion efficiency and Eddington ratio L = ε dM/dt c2 L = λ LEdd SimbolX, May 15, 2007

  21. Radiative Efficiency and Fraction of Eddington luminosity • Determine locus in ε-λ plane where there is the best match between local and relic BHMF! • ε=0.04-0.10 λ=0.08-0.5 which are consistent with common ‘beliefs’ on AGNs • Effect of changing scattering efficiency to compute pure reflection spectra of Compton-Thick sources CT space density degenerates with accretion efficiency and geometry of reflecting thick matter… 2% 0.5% 10% SimbolX, May 15, 2007

  22. Obscured AGN and SMBH census:observation strategies • A spectral survey of local CT Seyfert 2 galaxies previously discovered by BeppoSAX, INTEGRAL Swift and Suzaku. This should be accompanied by a volume limited survey of IR-bright or OIII-bright or … galaxies which have not shown strong X-ray emission below 10 keV, to search for highly CT objects. • A spectral survey of moderately obscured luminous QSOs discovered by XMM, Chandra up to z~1 (High luminosity) • Deep observations to search for faint mildly CT AGN + serendipitous survey (high redshift) • A survey of candidate CT AGN selected using their infrared emission (Spitzer/Herschel). SimbolX, May 15, 2007

  23. Summary A large fraction of the 10-40 keV XRB (2/3 - 3/4) will be resolved at a limiting flux of ~ 6 x 10-15 cgs A major breaktrough is foreseen (compare with ROSAT and Chandra better than ASCA and BeppoSAX) A large population of CT AGN (as large as Cthin ?) is waiting to be discovered by sensitive hard ( > 10 keV) X-ray observations Statistically meaningful sample of the most obscured AGN over a broad range of fluxes and luminosities -> XLF and evolution, SMBH assembly and distribution, geometry of obscuring/reflecting gas, …

More Related