SURVEY CHALLENGES

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SURVEY CHALLENGES

• Kirpal Nandra
• Imperial College London

With help from Antonis Georgakakis, Elise Laird,
James Aird, and the AEGIS team.
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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)
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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 z1 as (1z)3 like SFH
• Low LX decline above z1
• All decline above z3-4

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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

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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

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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
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Cosmic variance is a big problem, so we need
wider surveys, right?
WRONG
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THE AGN COLOR-MAGNITUDE RELATION
Nandra et al. 2006
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DEEP VS WIDE
Nandra et al. sample (200ks)
Bright sources only (Bootes limit)
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DEEP VS WIDE
Miyaji correlation functions
DEEP2 redshifts 4 deg2 (Davis et al 2003)
Cosmic variance is not a sin!
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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
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HIGH Z LUMINOSITY FUNCTION
z3 luminosity function
LX1043-44.5 space density
Hasinger et al (2005)
Aird et al. (in prep poster)
Barger et al. (2005)
? Completeness corrections are crucial
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ASIDE ABOUT LOW Z EVOLUTION
Chandra 2-8 keV L (2-10) 1.5E44 at z1 Evolves
as (1z)3 from z0 to z1 (Barger et al. 2005)
New hard X-ray data at z0 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 (1z)1-2
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PHOTOMETRIC REDSHIFTS
AEGIS/CFHTLS photo-zs (Ilbert et al. 2006)
Field dz/(1z) 0.05 Failure rate 5 X-ray
dz/(1z) 0.05 Catastrophic rate 10
? MUST ACCOUNT FOR PHOTO-Z ERRORS FAILURES IN
ANALYSIS!
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OPTICAL IDENTIFICATION
ID of SCUBA source GN11 (w/Alex Pope Douglas
Scott UBC)
HST/ACS
IRAC 3.6mm
radio
MIPS 24mm
Pope et al. c/part
Alexander et al X-ray c/part
? SCUBA AGN fraction may be lower than Alexander
et al. (2005)

• Chance projections in AEIGS to I25
• 7 IDs at 1.5 20 at 3 30 at 5
• REAL IDs are optically fainter ? high z?

? MAJOR IMPACT ON NUMBER OF HIGH Z AGN/REIONIZATON
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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
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PERILS OF HARDNESS RATIOS

• HRs overestimate the absorbed fraction and NH
  because NH cannot be lt0
• Especially bad at high z
• Simulations with ?1.9 and dispersion 0.2 and
  NH0!
• LBG at z3 with HR-1 actually has NH1.5E23

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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, its broad)
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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
  z3 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
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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?

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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 z1 as (1z)3 like SFH,, Low
  LX decline above z1, All decline above z3-4,
  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

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WHAT HAVE WE LEARNED FROM X-RAY SURVEYS?

• 0.5-5 keV XRB mostly resolved into AGN

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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?

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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

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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

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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.

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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.
  Spitzers 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)

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CURRENT AND TARGET DEPTHS