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

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

Chandra Surveys workshop : Survey Challenges WHAT HAVE WE LEARNED FROM X-RAY SURVEYS (1)? 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 L X decline above z=1 All decline above z~3-4

Chandra Surveys workshop : Survey Challenges WHAT HAVE WE LEARNED (2)? Type I/II fraction increases with L X 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 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 COSMIC VARIANCE Gilli et al. and Barger et al. noted z spikes in CDFs Georgakakis et al. GWS ~300 arcmin 2 Laird et al. AEGIS ~2000 arcmin 2

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

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

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

Chandra Surveys workshop : Survey Challenges DEEP VS WIDE DEEP2 redshifts ~4 deg 2 (Davis et al 2003) Miyaji correlation functions “Cosmic variance” is not a sin!

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

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

Chandra Surveys workshop : Survey Challenges 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) ASIDE ABOUT LOW Z EVOLUTION Implies evolution more like (1+z) 1-2 New hard X-ray data at z=0 RXTE XSS 3-20 keV L* (2-10) = 5.E43 (Sazonov) Integral keV L*(2-10)=6.0E43 (Beckmann) Integral keV L*(2-10)=3.5E43 (Sazonov) Swift BAT keV L*(2-10)=4.3E43

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

Chandra Surveys workshop : Survey Challenges OPTICAL IDENTIFICATION 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? ID of SCUBA source GN11 (w/Alex Pope + Douglas Scott UBC) HST/ACSIRAC 3.6mmradioMIPS 24mm Alexander et al X-ray c/part Pope et al. c/part  MAJOR IMPACT ON NUMBER OF HIGH Z AGN/REIONIZATON  SCUBA AGN fraction may be lower than Alexander et al. (2005)

Chandra Surveys workshop : Survey Challenges X-RAY INCOMPLETENESS 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 Georgakakis et al., in prep

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

Chandra Surveys workshop : Survey Challenges A type II AGN is one without broad lines in its optical spectrum A NOTE ON TYPE II QSOs 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 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 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 WHAT HAVE WE LEARNED FROM X-RAY SURVEYS? 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 L X decline above z=1, All decline above z~3-4, little reionization contribution Type I/II fraction increases with L X 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 WHAT HAVE WE LEARNED FROM X-RAY SURVEYS? keV XRB mostly resolved into AGN

Chandra Surveys workshop : Survey Challenges 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 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 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 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 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 deg 2 )? All-sky (RXTE, BAT, Integral, eRosita)

Chandra Surveys workshop : Survey Challenges CURRENT AND TARGET DEPTHS SurveyAreaDepthTargetExpo CDF-N0.12Ms5Ms3Ms CDF-S0.11Ms5Ms4Ms E-CDFS0.3250ks500ks1.5Ms AEGIS0.6200ks500ks2.4Ms COSMOS2(0.7)200ks 5Ms FLS5020ks1.5Ms Bootes95ks20ks1.8Ms SWIRE50Patchy20ks6Ms SDSS Eq25002ks6Ms