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The Chandra survey of the COSMOS field

The Chandra survey of the COSMOS field. Fabrizio Fiore & the C-COSMOS team Particular thanks to T. Aldcroft, M. Brusa, N. Cappelluti, F. Civano , A. Comastri, M. Elvis, S. Puccetti, C. Vignali , G. Zamorani M. Salvato & S-COSMOS team & many others. Table of content.

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The Chandra survey of the COSMOS field

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  1. The Chandra survey of the COSMOS field Fabrizio Fiore & the C-COSMOS team Particular thanks to T. Aldcroft, M. Brusa, N. Cappelluti, F. Civano, A. Comastri, M. Elvis, S. Puccetti, C. Vignali, G. Zamorani M. Salvato & S-COSMOS team & many others

  2. Table of content • Presentation of the survey • C-COSMOS in a context • Selected scientific results • Close pairs • High-z QSOs • Fraction of obscured AGN • Summary (what you should bring home after all..) • Multiwavelength coverage is mandatory • X-ray is the leading band for all AGN studies (provided that X-ray coverage is deep enough)

  3. The C-COSMOS survey: which science • Black hole growth and census • XMM has ~20% of ambiguous identifications. Chandra survey secures the discovery and identifications of rare objects (elusive AGN, high-z AGN). • The combination of Chandra data and Spitzer’s 24m and 3-8 m data allows us to unveil highly obscured accretion, thus providing a complete census of accreting SMBH • The influence of the environment on galaxy activity • excesses of X-ray point sources (AGN) within a few Mpc of clusters at 0.2<z<1. • spikes in the redshift distribution of the X-ray sources • The AGN and galaxy ACF and CCF down to a few arcsec: how the AGNs trace the cosmic web. • AGN pairs with separation<10-20”: galaxy activity vs. galaxy interaction

  4. The C-COSMOS survey: how • The Chandra high resolution permits to resolve sources 2” apart over 0.9 sq. deg., corresponding to 8-16 kpc separations for z = 0.3-0.9, and locates point sources to < 4 kpc at any z. Thus close mergers can be resolved, and AGNs can be distinguished from ULXs and off-nuclear starbust. • Thanks to the good PFS, ACIS-I is not background limited, then C-COSMOS reaches ~3 times deeper than XMM-COSMOS in both hard and soft bands and cross the threshold where starburst galaxies become common in X-rays. • The low ACIS background enables stacking analysis, in which counts at the positions of known classes of objects are co-added to increase the effective exposure time

  5. HST ACS imaging with resolution 0.05” and sensitivity 27.2 mag (10 ) provides morphologies of over 2 milions galaxies at < 100 pc resolution! Optical spectroscopy surveys: zcosmos:540 hours on the ESO VLT using VIMOS. Magellan COSMOS VLA-Cosmos Large Projectplus submm IR/Optical/UV large surveysto improve photometric redshift XMM-Newton: 1.4 Msec. Chandra! Cycle 8 proposal • 1.8 Msec • 200ksec • 0.9sq.deg • flim ~2x 10-16 cgs (0.5-2 keV) Spitzer: IRAC-deep MIPS-Shallow MIPS-Deep C-COSMOS in a context

  6. z = 0.73 structure 40 arcmin 52 arcmin z-COSMOS faint Full COSMOS field Color: XMM first year C-COSMOS: numbers Elvis et al. 2008 • 1.8 Ms total exposure time • 36 ACIS-I pointings • 200 ksec average exposure 0.5deg2 • 100 ksec average exposure 0.4deg2 • Flim~2x10-16 cgs (0.5-2 keV) • 1759 X-ray sources (probability threshold 2x10-5)

  7. Extreme AGN 5% Obscured AGN unobscured AGN SFgalaxies XBONGs Star XMM-COSMOS limit on1deg2 The C-COSMOS multiwavelenth catalog Civano et al 2008 • Identification in the 3.6micron K, and I bands using a statistical method to match the X-ray error box to the most likely cp (“likelihood ratio technique”) • “identification” in 3 bands sample: 94% !! • IR “identified” sample 5% • most interesting sources • high-z QSOs, obscured QSOs • ambiguous/unidentified sample 1% • 870 sources in common with XMM 895 NEW sources!! • 450 spectroscopic redshift already in hand(SDSS,VIMOS,IMACS) • Photometric redshift already available for 60% of the sample

  8. Close pairs Thanks to the good Chandra PSF it is possible to study close pairs to search for X-rays from galaxy interactions. Wavelet detection algorithm (PWDETECT, Damiani et al.) optimized to resolve nearby sources (Puccetti et al. 2008). A total of 106 sources closer than 12” are present in the X-ray catalog. > than expected from simulation. Next step is to obtain the spectroscopic identification to verify the fraction of physical pairs (Vignali et al. 2008)

  9. Chandra/XMM comparison BLUE circles= 0.5-7 keV chandra detections. Green =XMM contours 50% of the chandra pairs have associated only one XMM source. In several cases the brightness of the sources of the pair is similar.

  10. High redshift AGN • XMM-COSMOS: • QSO z>3 ~30 deg2 • QSO z>4 ~3 deg2 • Chandra ~3 times deeper than XMM • 100-200 QSO z>3 deg2 • 10-20 QSO z>4 deg2 C-COSMOS XMM-COSMOS Elvis et al. 2008 Brusa et al. 2008 Civano et al. 2008

  11. Non type 1 AGN MIR/O>1000 Type 1 AGN Chandra U ACS K 3.6m 4.5m Obscured AGN High X/O, high MIR/O

  12. 42-43 43-44 44-44.5 44.5-45.5 >45.5 AGN density La Franca, Fiore et al. 2005 Menci, Fiore et al. 2008 Paucity of Seyfert like sources @ z>1 is real? Or, is it, at least partly, a selection effect? Are we missing in Chandra and XMM surveys highly obscured (NH1024 cm-2) AGN? Which are common in the local Universe…

  13. Central engine Dusty torus Why multiwavelength surveys • IR surveys: • AGNs highly obscured at optical and X-ray wavelengths shine in the MIR thanks to the reprocessing of the nuclear radiation by dust

  14. Why multiwavelength surveys • Use both X-ray and MIR surveys: • Select unobscured and moderately obscured AGN in X-rays • Add highly obscured AGNs selected in the MIR • Simple approach: Differences are emphasized in a wide-band SED analysis

  15. MIR selection of CT AGN Fiore et al. 2003 ELAIS-S1 obs. AGN ELAIS-S1 24mm galaxies HELLAS2XMM CDFS obs. AGN Unobscured obscured MIR/O Open symbols = unobscured AGN Filled symbols = optically obscured AGN * = photo-z X/0

  16. MIR selection of CT AGN Fiore et al. 2008a Fiore et al. 2008b CDFS X-ray HELLAS2XMM GOODS 24um galaxies COSMOS X-ray COSMOS 24um galaxies R-K Open symbols = unobscured AGN Filled symbols = optically obscured AGN * = photo-z

  17. COSMOS MIR AGN Stack of Chandra images of MIR sourcesnot directlydetected in X-rays Fiore et al. 2008b

  18. AGN fraction Chandra survey of the Bootes field (5ks effective exposure) Brand et al. 2006 assume that AGN populate the peak at F24um/F8um~0 only. They miss a large population of obscured AGN, not detected at the bright limits of their survey.

  19. No AGN feedback AGN feedback Gilli et al. 2007 model La Franca et al. 2005 CT AGN volume density A B C GCH 2007 logNH>24 z=1.2-2.2: density IR-CT AGN ~ 45% density X-ray selected AGN, ~90% of unobscured or moderately obscured AGN z=0.7-1.2: density IR-CT AGN ~ 100% density X-ray selected AGN, ~200% of unobscured or moderately obscured AGN The correlation between the fraction of obscured AGN and their luminosity holds including CT AGN, and it is in place by z~2

  20. Density of Obscured AGNs ? ? Dashed lines = Menci model, no AGN feeback Solid lines = Menci model, AGN feedback 2-10 keV data = La Franca, FF et al. 2005 Spectroscopic confirmation: very difficult for the CDFS-GOODS sources (R~27, F(24um)~100uJy Possible for the COSMOS sources!! F24um~1mJy ==> Spitzer IRS AO5 program (Pri. C, Salvato et al.)

  21. Summary • Chandra sensitive survey of the COSMOS field: 1758 sources, ~half new, I.e. not detected by XMM • ~100 sources with optical counterpart fainter than I=26.5: ==> highly obscured QSOs, high-z QSOs • Large sample of bright pairs: ==> galaxy interaction vs. galaxy activity • Combined use of Chandra and Spitzer over a large field: ==> discovery of CT type 2 QSOs at z=1-2 ==> fraction of X-ray detected and X-ray emitting AGN in 24um samples is large (~50%) • All this will allow a precise determination of the evolution of the accretion in the Universe, a precise census of accreting SMBH • While multiwavelength coverage is mandatory, X-ray is the leading band for AGN studies (provided that X-ray coverage is deep enough)

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