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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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SURVEY CHALLENGES

Jan 14, 2016

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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. - PowerPoint PPT Presentation
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Page 1: SURVEY CHALLENGES

SURVEY CHALLENGES

Kirpal NandraImperial College London

With help from… Antonis Georgakakis, Elise Laird, James Aird, and the AEGIS team….

Page 2: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

THE AEGIS SURVEY

• 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)

aegis.ucolick.org

Page 3: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

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

Page 4: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

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

Page 5: SURVEY CHALLENGES

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

Page 6: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

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

Page 7: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

Cosmic variance is a big problem, so we need wider

surveys, right?

WRONG…

Page 8: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

Nandra et al. 2006

THE AGN COLOR-MAGNITUDE RELATION

Page 9: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

Bright sources only (~Bootes limit)

DEEP VS WIDE

Nandra et al. sample (200ks)

Page 10: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

DEEP VS WIDE

DEEP2 redshifts ~4 deg2

(Davis et al 2003)

Miyaji correlation functions

“Cosmic variance” is not a sin!

Page 11: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

X-RAY SOURCE ENVIRONMENTS

vs. host luminosity vs. host colour

Comparing with galaxies samples same range of LSS

AEGIS: Georgakakis et al. (2006) also Coil talk

Page 12: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

HIGH Z LUMINOSITY FUNCTION

z=3 luminosity function LX=1043-44.5 space density

Aird et al. (in prep + poster)Hasinger et al (2005)

Barger et al. (2005)

Completeness corrections are crucial

Page 13: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

Chandra 2-8 keV L* (2-10) = 1.5E44 at z=1Evolves 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=0RXTE 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

Page 14: SURVEY CHALLENGES

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!

Page 15: SURVEY CHALLENGES

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/ACS IRAC 3.6mm radioMIPS 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)

Page 16: SURVEY CHALLENGES

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

Page 17: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

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

Page 18: SURVEY CHALLENGES

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)

Page 19: SURVEY CHALLENGES

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- approachBut remember flux limits…

Page 20: SURVEY CHALLENGES

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?

Page 21: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

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

Page 22: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

WHAT HAVE WE LEARNED FROM X-RAY SURVEYS?

• 0.5-5 keV XRB mostly resolved into AGN

Page 23: SURVEY CHALLENGES

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?

Page 24: SURVEY CHALLENGES

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

Page 25: SURVEY CHALLENGES

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

Page 26: SURVEY CHALLENGES

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.

Page 27: SURVEY CHALLENGES

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 deg2)? • All-sky (RXTE, BAT, Integral, eRosita)

Page 28: SURVEY CHALLENGES

Chandra Surveys workshop : Survey Challenges

CURRENT AND TARGET DEPTHS

Survey Area Depth Target Expo

CDF-N 0.1 2Ms 5Ms 3Ms

CDF-S 0.1 1Ms 5Ms 4Ms

E-CDFS 0.3 250ks 500ks 1.5Ms

AEGIS 0.6 200ks 500ks 2.4Ms

COSMOS 2(0.7) 200ks 200ks 5Ms

FLS 5 0 20ks 1.5Ms

Bootes 9 5ks 20ks 1.8Ms

SWIRE 50 Patchy 20ks 6Ms

SDSS Eq 250 0 2ks 6Ms