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Introduction to the X-ray background Chandra Deep Field-North data Source Redshifts Diversity of X-ray selected sources

The 2Ms Chandra Deep Field-North. Introduction to the X-ray background Chandra Deep Field-North data Source Redshifts Diversity of X-ray selected sources Constraints on AGN evolution AGNs and binary AGNs in submm galaxies Future Directions. D. M. Alexander (IoA),

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Introduction to the X-ray background Chandra Deep Field-North data Source Redshifts Diversity of X-ray selected sources

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  1. The 2Ms Chandra Deep Field-North Introduction to the X-ray background Chandra Deep Field-North data Source Redshifts Diversity of X-ray selected sources Constraints on AGN evolution AGNs and binary AGNs in submm galaxies Future Directions • D. M. Alexander (IoA), • F. E. Bauer, W. N. Brandt (PSU), • A. E. Hornschemeier (JHU), • J. Barger (Wisc/IfA), • L. L. Cowie (IfA), • and C. Vignali (Bologna) • G. P. Garmire and D. P. Schneider (PSU) 2 Ms CDF-N (and 1 Ms CDF-S) catalogs are in Alexander et al. (2003) See http://www.astro.psu.edu/user/niel/hdf-chandra.html

  2. Introduction to the X-ray background

  3. Cosmic Background Radiation CXB: first background discovered (e.g., Giacconi et al. 1962)

  4. G~1.4 0.5-10.0 keV The Cosmic X-ray Background (Comastri et al. 1995) ROSAT: ~70% of 0.5-2.0 keV b/gd resolved ASCA/SAX: ~30% of 2-10 keV b/gd resolved Finding mostly unobscured AGNs (G~2.0)

  5. Chandra XMM-Newton Weisskopf et al. (2000) Jansen et al. (2001) Launched July 1999 ~0.1-10.0 keV band sensitivity Unsurpassed 0.”5 spatial resolution 4 mirrors (1145 cm2) 16.’9x16.’9field of view Launched December 1999 ~0.1-12.0 keV band sensitivity 5” spatial resolution 58 mirrors (4300 cm2) ~30’field of view The New Generation of X-ray Observatories

  6. The 2Ms Chandra Deep Field-North

  7. ~50 times deeper than deepest ROSAT survey ~250 times deeper than deepest ASCA survey Alexander et al. (2003) Deepest X-ray survey in 0.5-8.0 keV band See also talks by Comastri, Georgantopoulos, Green, and Mainieri Deep enough to detect mod.lum starbursts at z~1 and mod.lum AGNs at z~6

  8. “True” color image 0.5-2.0 keV 2.0-4.0 keV4.0-8.0 keV 1.945 Ms ACIS-I exposure (447 arcmin2 ) Still photon limited near the aim point 20 observations spanning 27 months 80-95% of 0.5-2 keV 70-90% of 2-8 keV HDF-N Alexander et al. (2003)

  9. +78 supplementary sources 503 main independent sources +6 extended sources Bauer et al. (2002) Alexander et al. (2003) One count detected every 6 days! Scores on the Doors…

  10. “True” color image 0.5-2.0 keV 2.0-4.0 keV4.0-8.0 keV 1.945 Ms ACIS-I exposure (447 arcmin2 ) SCUBA (sub-mm) GOODS survey (ACS+SIRTF) ISOCAM (mid-IR) 20 observations spanning 27 months 80-95% of 0.5-2 keV 70-90% of 2-8 keV HDF-N Deep optical-near-IR, and radio observations over whole field ~1000 spectroscopic redshifts Alexander et al. (2003)

  11. HST ACS 3/5 Epochs 18000x24000 pixels F850LP (z) F775W (i) F606W (V) F435W (B) 6” 3” 7.5” GOODS survey (ACS+SIRTF) 2.5” P.I.: M. Giavalisco Created by A. Koekemoer and Z. Levay Astrometry by S. Casertano and R. Hook Verification by M. Giavalisco, H. Ferguson, A. Koekemoer, M. Dickinson, N. Grogin, S. Ravindranath, T. Dahlen, and GOODS/ACS team

  12. Source Redshifts

  13. Optical data from the Subaru telescope (Capak et al. 2003) 503 Chandra sources (56% with redshifts) Redshifts mostly from the Keck telescope (Barger et al. 2003) Optical and Redshift Data Spec-z are challenging even for 8-10m telescopes Spec-z

  14. Barger et al. (2003) Redshift Distribution Spec-z Phot-z Majority of the sources lie at low-z; taking account of incompleteness is unlikely to significantly raise the z-peak

  15. Barger et al. (2003) Peaks in the Redshift Distribution Optical cluster (Dawson et al. 2001) and infrared redshift peak at z~0.85 FRI radio galaxy (Richards et al. 1999), and extended X-ray emission (Bauer et al. 2002) at z~1.01 Biasing due to large scale structure? See also Gilli et al. (2003) Similar peaks seen in the optical and infrared (e.g., Cohen et al. 2000)

  16. Diversity of X-ray selected sources AGNs, starbursts, and galaxies

  17. X-ray-to-optical flux ratio diagram Broad range of optical magnitudes at faint X-ray fluxes could suggest a variety of different source types

  18. Barger et al. (2002) Alexander et al. (2001) Barger et al. (2002) Barger et al. (2002) AGN source diversity AGN source density ~5000 deg-2: ~10 times higher than the deepest optical surveys X-rays provide a very efficient route to identifying AGNs and are relatively insensitive to absorption

  19. Bauer et al., in prep. Column density distribution determined via X-ray spectral analyses of 320/503 bright sources Many obscured AGNs are detected and the 183 fainter sources appear to be heavily obscured AGN source diversity Very few Compton-thick AGNs (~30: Alexander et al. 2003)

  20. Column density distribution determined via X-ray spectral analyses of 320/503 bright sources Many obscured AGNs are detected and the 183 fainter sources appear to be heavily obscured AGN source diversity Only a few obscured QSOs are identified: they are either rare or mostly exist at fainter fluxes Very few Compton-thick AGNs (~30: Alexander et al. 2003)

  21. Hornschemeier et al. (2003) Bauer et al. (2002) Normal Galaxies Starburst Galaxies Starbursts and Normal galaxies Evidence for X-ray detected galaxies: infrared, radio, optical, and X-ray (e.g., Alexander et al. 2002; Bauer et al. 2002; Hornschemeier et al. 2003)

  22. Hornschemeier et al. (2003) Starbursts and Normal galaxies Normal galaxies may dominate the source counts at very faint X-ray fluxes (Miyaji & Griffiths 2002; Hornschemeier et al. 2003)

  23. Brandt et al. (2001) Brandt et al. (2001) Stacking sources below the detection limit This technique has been successful in detecting average X-ray emission from these other source populations: EROs (Alexander et al. 2002; Brusa et al. 2002) Normal galaxies out to z~1 (Hornschemeier et al. 2002; Nandra et al. 2002) See Brusa talk for more details on ERO constraints Stacking 24 individually undetected z=2-4 Lyman-break galaxies, an overall X-ray detection was achieved! Average X-ray luminosity is comparable with that of a luminous starburst galaxy (e.g., NGC 3256)

  24. Contributions to the cosmic background 15 micron (IR) background (~70%): ~15% from AGNs (Alexander et al. 2002; Fadda et al. 2002) ~85% from starbursts/galaxies 0.5-8.0 keV background (~70-95%): Close to 100% from AGNs (many obscured) 2-5% from starbursts/galaxies 850 micron (submm) background: ~15% from AGNs (Barger et al. 2001) but many bright submm galaxies host an AGN (Alexander et al. 2003) ~85% from starbursts/galaxies

  25. Accretion Activity in the Universe AGN evolution

  26. Cowie et al. (2003) The cosmic evolution of AGNs AGN evolution is a function of the luminosity of the AGN => moderate-luminosity activity peaks at lower-z than high-luminosity activity (see also Fiore et al. 2003; Hasinger et al. 2003)

  27. Cowie et al. (2003) CDF-N Barger et al. (2003) SDSS The cosmic evolution of AGNs Less high-z AGNs than many models predicted; too few to re-ionise the Universe (see also Alexander et al. 2001 and Cristiani et al. 2003) See Brandt talk for properties of z>4 AGNs AGN evolution is a function of the luminosity of the AGN => moderate-luminosity activity peaks at lower-z than high-luminosity activity (see also Fiore et al. 2003; Hasinger et al. 2003)

  28. X-ray detected submm sources AGNs in dusty starburst galaxies Moderately deep Chandra surveys reported little overlap with the submm source population (e.g., Fabian et al. 2000; Severgnini et al. 2000; Hornschemeier et al. 2000, 2001; Barger et al. 2001)… What is the picture for a deep Chandra survey?

  29. 850 micron SCUBA image Borys et al. (2003) AGNs in submm galaxies 13 S/N>4 SCUBA galaxies detected with f(850um)>5 mJy (Borys et al. 2003)

  30. 850 micron SCUBA image Borys et al. (2003) 7 (54%) of the sources are X-ray detected (Alexander et al. 2003) AGNs in submm galaxies

  31. 850 micron SCUBA image Borys et al. (2003) 7 (54%) of the sources are X-ray detected (Alexander et al. 2003) AGNs in submm galaxies AGNs? At least 5 are AGNs (38% of bright submm galaxies) => almost all appear to be Compton-thin moderate-luminosity AGNs Given that only ~50% of local AGNs are Compton-thin (i.e., Risaliti et al. 1999), most (if not all) bright submm galaxies may contain an accreting SMBH AGNs are not luminous enough to power the submm emission

  32. Komossa et al. (2003) ~1kpc NGC6240 ~20kpc ~20kpc Alexander et al. (2003) Alexander et al. (2003) Binary AGNs? 2/7 (30%) submm galaxies with close X-ray pairs (<3”) vs 5/193 (3%) over whole field (see also Smail et al. in prep) This phenomena seems to be more closely linked to submm galaxies

  33. Future Directions

  34. Deeper vs Wider • Why Go Deeper? • Discovery space (still approx. photon limited) • Detect more Compton-thick AGNs • Improve X-ray spectral analysis • Detect more galaxies • Why Go Wider? • Detect rarer source types (e.g., obscured QSOs, high-z AGNs) • Improve statistics on AGN evolution/luminosity function • Trace both obscured and unobscured AGN evolution • Uncover extent of large-scale structure (i.e., redshift peaks)

  35. Summary • Resolved close to 100% of the 0.5-8.0 keV background: • most sources lie at at z<1 • peaks in z-distribution suggest large-scale structure effects • Broad variety of source types are detected: • optically (and X-ray) obscured and unobscured AGNs • starburst and normal galaxies • stars, galaxy groups and clusters • stacking analyses provides constraints on sources below detection limit • Efficient (and mostly absorption independent) AGN selection: • AGN source density >10 times larger than in optical (~5000 deg-2) • but few Compton thick AGNs are detected (further AGNs to be found?) • Mod-lum AGNs dominant at low-z, contrary to high-lum AGNs • Many (all?) bright submm galaxies contain an AGN/binary AGN For all papers and data products (CDF-N and CDF-S): http://www.astro.psu.edu/user/niel/hdf-chandra.html

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