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SURVEY CHALLENGES

SURVEY CHALLENGES. Kirpal Nandra Imperial College London. With help from… Antonis Georgakakis, Elise Laird, James Aird, and the AEGIS team…. THE AEGIS SURVEY. aegis.ucolick.org. Chandra: 1.6 Ms over 0.5 deg 2 DEEP II spectroscopy HST, Spitzer, VLA, GALEX, CFHT LS blah blah blah.

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SURVEY CHALLENGES

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  1. SURVEY CHALLENGES Kirpal Nandra Imperial College London With help from… Antonis Georgakakis, Elise Laird, James Aird, and the AEGIS team….

  2. THE AEGIS SURVEY aegis.ucolick.org • Chandra: 1.6 Ms over 0.5 deg2 • DEEP II spectroscopy • HST, Spitzer, VLA, GALEX, CFHT LS blah blah blah “AEGIS” ApJL special issue (~20 papers accepted) Chandra Surveys workshop : Survey Challenges

  3. WHAT HAVE WE LEARNED FROM X-RAY SURVEYS (1)? • 0.5-5 keV XRB mostly resolved into AGN • Fainter soft sources high z starbursts • X-rays detect more AGN than optical • Additional Compton thick AGN provide 30 keV background • Evolution: • Rapid evolution to z=1 as (1+z)3 like SFH • Low LX decline above z=1 • All decline above z~3-4 Chandra Surveys workshop : Survey Challenges

  4. WHAT HAVE WE LEARNED (2)? • Type I/II fraction increases with LX • But still many type II QSOs • The type I/II fraction decreases with z • AGN associated/coeval with star formation • Host galaxies: red, massive, bulge dominated • Clustering like hosts, perhaps even more Chandra Surveys workshop : Survey Challenges

  5. SO WHAT ARE THE CHALLENGES? • Cosmic variance i.e. large scale structure • Optical completeness and Identification • X-ray completeness and analysis issues • Statistical biases and small number stats • Selection methods and biases Chandra Surveys workshop : Survey Challenges

  6. COSMIC VARIANCE Gilli et al. and Barger et al. noted z spikes in CDFs Georgakakis et al. GWS ~300 arcmin2 Laird et al. AEGIS ~2000 arcmin2 Chandra Surveys workshop : Survey Challenges

  7. Cosmic variance is a big problem, so we need wider surveys, right? WRONG… Chandra Surveys workshop : Survey Challenges

  8. THE AGN COLOR-MAGNITUDE RELATION Nandra et al. 2006 Chandra Surveys workshop : Survey Challenges

  9. DEEP VS WIDE Nandra et al. sample (200ks) Bright sources only (~Bootes limit) Chandra Surveys workshop : Survey Challenges

  10. DEEP VS WIDE Miyaji correlation functions DEEP2 redshifts ~4 deg2 (Davis et al 2003) “Cosmic variance” is not a sin! Chandra Surveys workshop : Survey Challenges

  11. X-RAY SOURCE ENVIRONMENTS vs. host luminosity vs. host colour AEGIS: Georgakakis et al. (2006) also Coil talk Comparing with galaxies samples same range of LSS Chandra Surveys workshop : Survey Challenges

  12. HIGH Z LUMINOSITY FUNCTION z=3 luminosity function LX=1043-44.5 space density Hasinger et al (2005) Aird et al. (in prep + poster) Barger et al. (2005)  Completeness corrections are crucial Chandra Surveys workshop : Survey Challenges

  13. ASIDE ABOUT LOW Z EVOLUTION Chandra 2-8 keV L* (2-10) = 1.5E44 at z=1 Evolves as (1+z)3 from z=0 to z=1 (Barger et al. 2005) New hard X-ray data at z=0 RXTE XSS 3-20 keV L* (2-10) = 5.E43 (Sazonov) Integral 20-40 keV L*(2-10)=6.0E43 (Beckmann) Integral 17-60 keV L*(2-10)=3.5E43 (Sazonov) Swift BAT 10-100 keV L*(2-10)=4.3E43 Implies evolution more like (1+z)1-2 Chandra Surveys workshop : Survey Challenges

  14. PHOTOMETRIC REDSHIFTS AEGIS/CFHTLS photo-z’s (Ilbert et al. 2006) Field: dz/(1+z) = 0.05 Failure rate = 5% X-ray: dz/(1+z) = 0.05 Catastrophic rate =10%  MUST ACCOUNT FOR PHOTO-Z ERRORS FAILURES IN ANALYSIS! Chandra Surveys workshop : Survey Challenges

  15. Chance projections in AEIGS to I=25: 7% IDs at 1.5”; 20% at 3”; 30% at 5” REAL IDs are optically fainter  high z? OPTICAL IDENTIFICATION ID of SCUBA source GN11 (w/Alex Pope + Douglas Scott UBC) HST/ACS IRAC 3.6mm MIPS 24mm radio Pope et al. c/part Alexander et al X-ray c/part  SCUBA AGN fraction may be lower than Alexander et al. (2005)  MAJOR IMPACT ON NUMBER OF HIGH Z AGN/REIONIZATON Chandra Surveys workshop : Survey Challenges

  16. X-ray images are Highly inhomogeneous In poisson regime Source detection “black box” (e.g. wavdetect) Detection inconsistent with sensitivity Eddington bias, poisson noise, incompleteness Embodied in sensitivity curve X-RAY INCOMPLETENESS Georgakakis et al., in prep Chandra Surveys workshop : Survey Challenges

  17. PERILS OF HARDNESS RATIOS • HRs overestimate the absorbed fraction and NH because NH cannot be <0 • Especially bad at high z • Simulations with =1.9 and dispersion 0.2 and NH=0! • LBG at z=3 with HR=-1 actually has NH=1.5E23 Chandra Surveys workshop : Survey Challenges

  18. A NOTE ON TYPE II QSOs A type II AGN is one without broad lines in its optical spectrum By this definition, no true type II QSOs have been found in X-ray surveys, as e.g. H is unobserved (and if it is, it’s broad) Chandra Surveys workshop : Survey Challenges

  19. DO X-RAY SURVEYS FIND ALL AGN? • Heckman et al. (2005) say OIII better at selecting local AGN than X-ray • Steidel et al. (2002) found 70% of X-ray AGN at z=3 LBGs from spectroscopy • Also one AGN X-ray undetected in 1 Ms • Sarajedini et al. (2006): 70% of optically variable nuclei X-ray undetected (200ks Chandra) • AEGIS (Renbin Yan, Berkeley): • 60% of X-ray sources have AGN line ratios • 10% have no OIII • Only 30% of line-ratio selected (candidate) AGN are X-ray sources! Not to mention Spitzer selection… need multi- approach But remember flux limits… Chandra Surveys workshop : Survey Challenges

  20. OTHER ISSUES • Separating AGN and starbursts • Is it reasonable to assume Compton thick evolve like unobscured • Is alpha_ox dependent on UV luminosity really? • How does variability affect SEDs. Dispersion? • Effects of variability effects on photoz? Chandra Surveys workshop : Survey Challenges

  21. WHAT HAVE WE LEARNED FROM X-RAY SURVEYS? • 0.5-5 keV XRB mostly resolved into AGN • Fainter soft sources high z starbursts • X-rays detect more AGN than optical • Additional Compton thick AGN provide 30 keV background • Rapid evolution to z=1 as (1+z)3 like SFH,, Low LX decline above z=1, All decline above z~3-4, little reionization contribution • Type I/II fraction increases with LX • But still many type II QSOs • The type I/II fraction decreases with z • AGN associated/coeval with star formation • Host galaxies: red, massive, bulge dominated • Clustering like hosts, perhaps even more Chandra Surveys workshop : Survey Challenges

  22. WHAT HAVE WE LEARNED FROM X-RAY SURVEYS? • 0.5-5 keV XRB mostly resolved into AGN Chandra Surveys workshop : Survey Challenges

  23. WHAT ARE THE IMPORTANT QUESTIONS? • How are AGN triggered? • Do they affect bulge/star formation, or vice versa? • What are the astrophysical processes implied by obscuration? • Do X-rays tell us anything useful about star formation? • AGN contribution to the total luminosity of the universe (c.f. stars)? • How do AGN affect the early universe? • Can clusters be used to constrain cosmology • What is the history of the baryons in the universe? Chandra Surveys workshop : Survey Challenges

  24. MSSTs • Impact of environment on galaxies • Are AGN created by mergers? • History of accretion • Physics geometry and evolution of absorption • Physics and evolution of groups ad clusers • Effect of AGN feedback on galaxy hosts, groups and clusters • Cluster mass function at high z and growth of structure Chandra Surveys workshop : Survey Challenges

  25. ANEWs • Generating and sharing data • All sky hard X-ray surveys • Followup of non X-ray obscured AGN • Deeper Chandra surveys • Better photoz • Large area cluster survey • Relevant Spitzer observations • Multiwavelength completeness corrections • Extend ultradeep surveys in areas with best NIR • X-ray surveys before Spitzer dies or JWST comes • Development of multivariate luminsity functions • Followup of variablity-selected objects Chandra Surveys workshop : Survey Challenges

  26. WAYS FORWARD? • Better analysis of existing data is possible (and needed) • Need to learn from each other • Archival and ground-based followup needed • And… more X-ray observations might be justified… so what observations do we need? • Infinite depth, 4pi area? • In reality each problem defines its own requirement in area-depth parameter space. Chandra Surveys workshop : Survey Challenges

  27. A (PROVOCATIVE) PROPOSAL • Certain fields deep Spitzer and wide HST • Cosmos, AEGIS, GOODS, E-CDFS/GEMS (Chandra) • There are only a few Spitzer wide fields • Bootes, FLS, SWIRE (XMM) • Need Spitzer for complete AGN selection. Spitzer’s cryogen is running out •  Concentrate on making these fields better, and make all the data public • Also need very wide fields: • Archival (2XMM, Champ, AXIS) • XMM slew survey of SDSS equatorial strip (250 deg2)? • All-sky (RXTE, BAT, Integral, eRosita) Chandra Surveys workshop : Survey Challenges

  28. CURRENT AND TARGET DEPTHS Chandra Surveys workshop : Survey Challenges

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