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Part IPart IAGN Surveys in Different Bands AGN Surveys in Different Bands AGN Surveys in different bands
– Retrospect – Optical selection and implications– Radio selection– Infrared selection– High-Energy selection
Selection Effects
Part IIPart IIAGN X-ray SurveysAGN X-ray Surveys
Soft X-rays SurveysHard X-ray Surveys
– Pre-Chandra and XMM-Newton– Deep Chandra and XMM-Newton Surveys
Deep Extragalactic X-ray Surveys2Ms Chandra Point-Source CATA
RetrospectRetrospect
Lamppost Effect– find something in where we can find it
Three types of surveys– Find object– Find object consistently– Find with well-defined selection criteria
RetrospectRetrospectFirst indication (optical)
– NGC1068-broad emission lines (Fath, 1913)– M87-jet (Curtis 1917)– Extragalactic radio sources– The origin of name for quasar (Schmidt et.al., 1
964)
Retrospect Retrospect Early AGN Surveys
– Cambridge xC Surveys– Markarian Survey– Zwichky Survey
Recent Large Surveys– 2dF– SDSS
How to find AGN-SED– Power law (1013Hz-1020Hz)– Highly ionized Emission lines-C N O– Low-ionization emission lines-Fe
Optical SelectionOptical Selection
Principle (Sandage 1971)– Systematic optical color deviation from starlight
Bonus– Photometric red-shift estimation
Declaration of “complete samples” Fatal bug
– Lb does not correlated well with Lgalaxy → cannot see low luminosity AGN in massive galaxies (contamination)
Aftermath– Omission (radio, IR, X-ray)
Optical selection effect– Luminosities– Hard to evaluate
Alternatives – Variability– Absence of proper motion
Optical SelectionOptical Selection
Radio SelectionRadio Selection Principles
– Flat-spectrum, compact radio source– Object with low IR/radio– morphology
Advantages – Efficient– Sensitive – Accurate – Find objects omitted by optical techniques
Disadvantages– Incomplete (selection effect)– Star-forming region
Infrared SelectionInfrared Selection
Disadvantages– Color difference is subtle– Equivalent width insufficient – An Island
Potential advantages– mid-IR to be a “pivot point” in SED– PAH and high ionization IR lines
Prospect– SIRTF
High-Energy SelectionHigh-Energy Selection
X-ray and γ-rayDisadvantages
– Soft X-ray suffer from larger extinction– Red-shift distribution– γ-ray position– Soft X-ray bias
Selection EffectSelection Effect
Dilution of the optical/IR brightness and color by the starlight.
ObscurationAnother selection effect
Advantages Advantages
Great sensitivity of Chandra and XMM-Newton
ACIS
(ergs-cm-2 sec-1 in 10 5 s)
HRC (ergs-cm-2 sec -1 in 10 5 s )
4×10-15 4×10-15
EPIC MOS
(ergs-cm-2 sec-1 in 10 5 s)
EPIC pn(ergs-cm-2 sec -1 in 10 5 s )
~ 4×10-14 ~ 4×10-14
Advantages Advantages
Accurate positions from Chandra– ~ 0.5 arcsec
Einstein EXOSAT ROSAT BBXRT/ASCA
Chandra XMM-Newton
4 18 4 75 0.5 20
Advantages Advantages
A relatively large fraction of the bolometric energy (3-20%) is radiated in the classical X-ray bands.
High area density (400 deg-2) Large amplitude and frequency of variability in
the X-ray band. Little Contamination from other objects High red-shift quasars are easy to detect Close to the black hole
Early X-ray SurveysEarly X-ray Surveys
Uhuru (1970 10-1973 3) [2-20 keV]Ariel-V (1973 10-1980 3) [0.3-40 keV]HEAO-1 (1977 8-1979 1) [0.2keV-10MeV]
Soft X-ray SurveysSoft X-ray Surveys
Einstein (1978 11-1981 4) [0.2-20 keV]ROSAT (1990 1-1999 2) [0.1-2.5 keV]
Hard X-ray surveysHard X-ray surveys
ASCA (1993 2-2001 3) [0.4-10 keV]BeppoSAX (1996 4-2002 4) [0.1-300 keV]Fruit
– ~ 500 serendipitous sources over ~ 100 deg2
Deep Deep ChandraChandra and and XMMXMM--NewtonNewton SurveysSurveys
Chandra (1999 7-present)XMM-Newton (1999 10-present)
Deep Deep ChandraChandra and and XMMXMM--NewtonNewton SurveysSurveys
Fruit– Numerous “optically dull” objects– Greatly enlarge the AGN population
Deep Extragalactic X-ray SurveysDeep Extragalactic X-ray Surveys
Source classification difficulties– Too faint to be identified by optical spectrum– Many of the X-ray sources have modest optical
luminosities, often due to obscuration– “schism” between optical (type1 and type2) and
X-ray (unobscured and obscured )
Deep Extragalactic X-ray SurveysDeep Extragalactic X-ray Surveys
Basic AGN Types– Unobscured AGN– Obscured AGN with clear optical/UV AGN sig
natures.– Optically faint X-ray sources– XBONGs
(X-ray Bright Optically Normal Galaxies)
AGN Red-shift DistributionAGN Red-shift Distribution
Most AGN in deep X-ray surveys have z =0~2
Redshift distribution show “spikes” in z=0.5~2.5
[Bargar et al. 2002] [Bargar et al. 2003]
AGN Selection CompletenessAGN Selection Completeness
Reasons of incompleteness– Compton thick AGN– Luminous at non-X-ray, but X-ray weak
How many we haven’t seen
2000-3000 deg-2
Key results from DEXSKey results from DEXS
Large optically selected luminous quasars– PLE (Pure luminosity Evolution)
Moderate-luminosity AGN– LDDE (luminosity-dependent density
evolution)
X-ray constraintsX-ray constraints
Sky density– Bottom line (z > 4) ~ 30-150 deg-2
– AGN contribution to reionization at z ~ 6 is small Accretion[z>4] ~ Accretion[local] Infrared and sub-millimeter
– star-forming processes AGN/sub-mm galaxies >=40%. X-ray survey should remain an effective way to fi
nd AGN at the highest redshift
Future prospectsFuture prospects
Detailed cosmic history of SMBH accretionThe nature of AGN activity in young,
forming galaxiesX-ray measurements of clustering and
large-scale structureThe X-ray properties of cosmologically
distant starburst and normal galaxies
The 2Ms CDF-NThe 2Ms CDF-N
Main CATAlog– High significant Chand
ra sources
Supplementary CATAlog
– Lower significance Chandra sources
20 observations
447.8 arcmin2
Flux limit=2.5×10-17 erg cm-2 s-1 (0.5-2.0 keV)
Flux limit=1.4 ×10-16 erg cm-2 s-1 (2.0-8.0 keV)
Data reductionData reduction
CIAO– Chandra Interactive
Analysis of Observations
Radiation damage Quantum Efficiency
Losses Bad column Bad pixel Cosmic ray afterglow Standard pixel
randomization Potential background
events
Production of CATAlogsProduction of CATAlogs
Technique feature – Matched filter
Accuracy of the X-ray source position
Correlation of optically bright sources with lower significance Chandra sources
Point-source DetectionPoint-source Detection
Key criterion
1×10-5
supplementary optically bright source CATAlog
False positive probability 1×10-7
main CATAlog
Supplementary Optically Supplementary Optically Bright Chandra Source CATABright Chandra Source CATA
X –ray Optical R-band 5.1
79 sources
ProspectsProspects
Doubling the exposure of a Chandra observation leads to an increase in sensitivity between and .
The number of background counts is often negligible.
Negative K-correction of absorbed AGN emission
2 2
Longer and longer