Heavily-Obscured Super-Massive Heavily-Obscured Super-Massive Black Holes at Low and High Black Holes at Low and High
RedshiftRedshift
Ezequiel Treister (IfA, Ezequiel Treister (IfA, HawaiiHawaii)
Meg Urry, Priya Natarajan, Carie Cardamone, Kevin Schawinski (Yale), Eric Gawiser (Rutgers), Dave Sanders
(IfA) and the MUSYC collaboration
Credit: ESO/NASA, the AVO project and Paolo Padovani
Active Galactic Nuclei Active Galactic Nuclei (AGN)(AGN)
Urry & Padovani, 1995
Black hole–galaxy Black hole–galaxy connectionconnection
All (massive) galaxies have All (massive) galaxies have black holesblack holes
Tight correlation of MBH with Common BH/SFR EvolutionAGN feedback important
All (Massive) GalaxiesAll (Massive) Galaxieshave super-massive black holeshave super-massive black holes
Black hole–galaxy Black hole–galaxy connectionconnection
All (massive) galaxies have black All (massive) galaxies have black holesholes
Tight correlation of MTight correlation of MBHBH with with Common BH/SFR EvolutionAGN feedback important
MMBHBH- - Correlation Correlation
Greene & Ho, 2006
Same relation for bothactive and non-active galaxies.
Black hole–galaxy Black hole–galaxy connectionconnection
All (massive) galaxies have black All (massive) galaxies have black holesholes
Tight correlation of MTight correlation of MBHBH with with Common BH/SFR EvolutionCommon BH/SFR EvolutionAGN feedback important
Common BH/Star Formation Common BH/Star Formation EvolutionEvolution
Marconi et al. 2004
Black hole–galaxy Black hole–galaxy connectionconnection
All (massive) galaxies have black All (massive) galaxies have black holesholes
Tight correlation of MTight correlation of MBHBH with with Common BH/SFR EvolutionAGN feedback importantAGN feedback important
AGN FeedbackAGN Feedback
Springel et al. 2005
No AGN
With AGN Feedback
Supermassive Black Supermassive Black Holes Holes
Credit: ESO/NASA, the AVO project and Paolo Padovani
Many obscured by gas and dustMany obscured by gas and dust
How do we know that?How do we know that?
Local AGN Unification
Explain Extragalactic X-ray “Background”
Observed X-ray Observed X-ray “Background”“Background”
Frontera et al. (2006)
AGN in X-raysAGN in X-rays
Increasing NH
Photoelectric absorptionaffect mostly low energy emission making the observed spectrum look harder.
X-ray BackgroundX-ray Background
Gilli et al., 2007
XRB well explained using a combination of obscured and unobscured AGN.
•Setti & Woltjer 1989•Madau et al. 1994•Comastri et al. 1995•Gilli et al. 1999,2001•Treister & Urry 2005•Gilli et al. 2007•And others…
Compton Thick AGNCompton Thick AGN Defined as obscured sources with
NH>1024 cm-2. Very hard to find (even in X-
rays). Observed locally and needed to
explain the X-ray background. Number density highly uncertain. May contribute significantly to
SMBH accretion. Multiwavelength observations are
required to find them. Hard X-rays (E>10keV) very useful
locally.
SwiftSwift INTEGRALINTEGRAL
ISDC
Swift Sources
Tueller et al. 2007
Significance Image, 20-50 keV
Deep INTEGRAL Survey (3 Msec)Deep INTEGRAL Survey (3 Msec)
Log N-Log SLog N-Log S
Treister et al. 2009
Log N-Log SLog N-Log S
Treister et al. 2009
Fraction of CT AGNFraction of CT AGN
Treister et al. 2009
X-ray background does not constrain density of CT AGN
X-Ray Background X-Ray Background SynthesisSynthesis
Treister et al. 2009
Contribution of CT AGN to the Contribution of CT AGN to the XRBXRB
Only 1% of the XRB comes from CT AGN at z≥2. We can increase the # of CT AGN by ~10x and still fit the XRB.
Only 1% of the XRB comes from CT AGN at z≥2. We can increase the # of CT AGN by ~10x and still fit the XRB.
Treister et al. 2009
CT AGN at High RedshiftCT AGN at High Redshift
Treister et al. 2009
NuSTARNuSTAR
How to find high-z CT AGN NOW?How to find high-z CT AGN NOW?
X-raysX-rays
Tozzi et al. 2006
Trace rest-frame higher energies at higher redshifts Less affected by obscurationTozzi et al. claimed
to have found 14 CT AGN (reflection dominated) candidates in the CDFS.Polletta et al. (2006) report 5 CT QSOs (transmission dominated) in the SWIRE survey.
Fiore et al. 2008
How to find high-z CT AGN NOW?How to find high-z CT AGN NOW?
Mid-IRMid-IR X-ray StackingX-ray Stacking
FF2424/F/FRR>1000>1000
FF2424/F/FRR<200<200
• 4 detection in X-ray stack. Hard spectral shape, harder than X-ray detected sources.Good CT AGN candidates.• Similar results found by Daddi et al. (2007)
Extended Chandra Deep Field-Extended Chandra Deep Field-SouthSouth
Area:Area: 0.3 deg2
X-rays:X-rays: Chandra 250ks/pointing
Optical:Optical: Broad band UBVRIz (V=26.5)+ 18 Medium band filters (to R=26)
Near-IR:Near-IR: JHK to K=20 (Vega)
Mid-IR:Mid-IR: IRAC 3.6-8 microns + MIPS 24 microns to 35 µJy
Spectroscopy:Spectroscopy: VLT/VIMOS, Magellan/IMACS (optical) VLT/SINFONI, Subaru/MOIRCS (near-IR)
Mid-IR SelectionMid-IR Selection
R-K (Vega)
- 211 sources with f24m/fR>1000 and R-K>4.5- f24m>35Jy- 18 X-ray detected
Treister et al. ApJ in press
Redshift DistributionRedshift Distribution
All Sources
X-ray Detected
X-ray Undetected- Photo-z for ~50% of the sources- X-ray sources brighter at all wavelengths- Spec-z for 3 X-ray sources and photo-z for 12 (83% complete).
Treister et al. ApJ in press
Hardness Ratio Hardness Ratio N NHH
X-ray sources with redshift onlyX-ray sources with redshift only
- 2 unobscured- 11 obscured Compton-thin- 2 Compton Thick
Assumed fixed =1.9
Treister et al. ApJ in press
Stacking of non-Xrays SourcesStacking of non-Xrays Sources
Soft (0.5-2 keV) Hard (2-8 keV)
- ~4 detection in each band.- fsoft=2.1x10-17erg cm-2s-1. Fhard= 8x10-17erg cm-2s-1
- Sources can be detected individually in ~10 Msec.- Hardness ratio 0.13, NH=1.8x1023cm-2.- Alternatively, ~90% CT AGN and 10% star-forming galaxies.- Some evidence for a flux dependence. >95% CT AGN at the brightest bin, 80% at the lowest. Large error bars.
Treister et al. ApJ in press
Rest-Frame StackingRest-Frame Stacking
Good fit with either NH1023cm-2 or combination of CT AGN with star-forming galaxies.
Consistent results with observed-frame stacking.
Treister et al. ApJ in press
X-Ray to Mid-IR RatioX-Ray to Mid-IR Ratio
Both X-rays and 12µm good tracers of AGN activity.Observed ratios for X-ray sources consistent with local AGN (dashed line).
Treister et al. ApJ in press
X-Ray to Mid-IR RatioX-Ray to Mid-IR Ratio
Effects of obscuration in X-ray band luminosity.
Only important for Compton Thick sources.
Treister et al. ApJ in press
X-Ray to Mid-IR RatioX-Ray to Mid-IR Ratio
~100x lower ratio for X-ray undetected sources.
Explained by NH~5x1024 to 1025cm-2
Treister et al. ApJ in press
X-Ray to Mid-IR RatioX-Ray to Mid-IR Ratio
Ratio for sources with L12µm>1043erg/s (~80% of the sources) ~2-3x higher than star-forming galaxies
Treister et al. ApJ in press
X-Ray to Mid-IR RatioX-Ray to Mid-IR RatioUsing Lx/L12µm=0.007 to separate AGN and star-forming galaxies ~80% AGN, consistent with HR value.
In sources with L12µm>1044erg/s outside selection region fraction of AGN ~10%.
Treister et al. ApJ in press
Near to Mid-IR ColorsNear to Mid-IR Colors- Distributions significantly different- X-ray detected sources much bluer- Average f8/f24=0.2 for X-ray sources and 0.04 for X-ray undetected sample
BluerRedder
Well explained by different viewing angle (30o vs 90o) in the same torus model Can it be star-formation versus AGN?
Treister et al. ApJ in press
Near to Mid-IR ColorsNear to Mid-IR Colors
Armus et al. 2007
ULIRG, LINER
ULIRG, Sey2
MorphologiesMorphologies
Ground based: K,H,R
HST/WFC3J,H,Y
GOODS-SUDF
Optical/Near-IR SED FittingOptical/Near-IR SED Fitting
X-ray Detected
X-ray Undetected
X-ray Detected
X-ray Undetected
- Median stellar mass for X-ray detected sources ~4.6x1011 Msun.- For X-ray undetected source ~1011 Msun.
- Mild extinction values found in general.- Maximum Av~4 mags.- Median E(B-V)=0.6 for X-ray detected sources and 0.4 for undetected ones.
Treister et al. ApJ in press
Evidence for significant recent star formation in most sources
Heavily-Obscured AGN Space Heavily-Obscured AGN Space DensityDensity
Systematic excess for Lx>1044erg/s sources relative to extrapolation of Compton-thin LF
Strong evolution in number of sources from z=1.5 to 2.5.
Consistent with heavily-obscured phase after merger?
Treister et al. ApJ in press
Obscured to Unobscured Quasar Obscured to Unobscured Quasar RatioRatio
Treister et al. in prep.
The Merger-Quasar ConnectionThe Merger-Quasar Connection
Treister et al. in prep.
Obscured quasars are the product of the merger of two massive gas-rich galaxies. After a time t the quasar becomes unobscured.
€
NobscNUnobsc
(z) =Δtd2merger
dtdNNgal (> Mmin (z)) fgas(z)
NUnobsc (z)
The Merger-Quasar ConnectionThe Merger-Quasar Connection
Treister et al. in prep.
t=7716 Myrs
SummarySummary
• Number of mildly CT sources at z~0 lower than expected.
• Only ~1% of XRB comes from CT AGN at z~2.• Multiwalength surveys critical to find high-z CT AGN.
• Mid-IR selection finds large number of CT AGN at z>1.5.
• Morphologies indicates interactions/mergers.
• Host galaxy masses ~1011 Msun with young and obscured stellar populations.
• Strong evolution in numbers up to z~3.• This could be evidence for a heavily obscured phase after quasar triggering.
• Number of mildly CT sources at z~0 lower than expected.
• Only ~1% of XRB comes from CT AGN at z~2.• Multiwalength surveys critical to find high-z CT AGN.
• Mid-IR selection finds large number of CT AGN at z>1.5.
• Morphologies indicates interactions/mergers.
• Host galaxy masses ~1011 Msun with young and obscured stellar populations.
• Strong evolution in numbers up to z~3.• This could be evidence for a heavily obscured phase after quasar triggering.