Download Common BH/SFR Evolution

Heavily Obscured
Supermassive Black Holes
Ezequiel Treister
Einstein Fellow
IfA, Hawaii
Collaborators: Meg Urry, Priya Natarajan, Carie Cardamone,
Kevin Schawinski (Yale), Eric Gawiser (Rutgers), Dave Sanders
(IfA) and the MUSYC team
Credit: ESO/NASA, the AVO project and Paolo Padovani
Active Galactic Nuclei (AGN)
Black hole:
106-108 Msun
Accretion disk:
~few light-days
Torus:
105-107 Msun
~few parsec
gas+dust
geometry unknown
Source of nuclear
obscuration
Urry & Padovani, 1995
AGN Emission
mm far-IR
near-IR Optical-UV
X-rays
Manners, 2002
Black hole–galaxy connection
All (massive) galaxies have
black holes
Tight correlation of MBH with 
Common BH/SFR Evolution
AGN feedback important
Milky Way SMBH
Mass: 4x106 Msun
All (Massive) Galaxies
have super-massive black holes
Black hole–galaxy connection
All (massive) galaxies have black
holes
Tight correlation of MBH with 
Common BH/SFR Evolution
AGN feedback important
MBH-  Correlation
Same relation for both
active and non-active
galaxies.
: stellar velocity
dispersion, measured
in the central region.
 indicates stellar
mass outside
influence radius of
BH.
Greene & Ho, 2006
Black hole–galaxy connection
All (massive) galaxies have black
holes
Tight correlation of MBH with 
Common BH/SFR Evolution
AGN feedback important
Common BH/Star Formation
Evolution
Redshift (z): receding
velocity due to expansion
of the Universe.
z=1
z=2
~50% of the
age of the
Universe,
7.7x109 light
years.
~80% of the
age
of the
Universe.
Marconi et al. 2004
Black hole–galaxy connection
All (massive) galaxies have black
holes
Tight correlation of MBH with 
Common BH/SFR Evolution
AGN feedback important
AGN Feedback
No AGN
With AGN
Feedback
Springel et al. 2005
QuickTime™ and a
decompressor
are needed to see this picture.
Unobscured
(naked)
Quasar
Obscured
Quasar
T~108years
Hopkins et al. (2008)
Obscured Accretion
• Critical stage of BH-galaxy connection.
• Occurs when galaxies form most of their stars.
• Can represent up to 50% of matter accretion
onto the central black hole.
How do we know that?
Credit: ESO/NASA, the AVO project and Paolo Padovani
Observed X-ray “Background”
Treister et al. 2009b
Resolving the X-ray
Background
AGN in X-rays
X-ray spectrum of
unobscured AGN much
softer than X-ray
background.
AGN in X-rays
Photoelectric absorption
affect mostly low energy
emission making the
observed spectrum
look harder.
AGN in X-rays
Compton 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 Xray background.
• Number density highly
uncertain.
Increasing NH
X-ray Background
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…
Treister et al. 2009b
Finding nearby obscured AGN
Swift
INTEGRAL
Swift Sources
ISDC
Tueller et al. 2010
Deep INTEGRAL Survey (3 Msec)
Significance Image, 20-50 keV
Deep INTEGRAL Survey (3 Msec)
Significance Image, 20-50 keV
Deep INTEGRAL Survey (3 Msec)
Significance Image, 20-50 keV
Fraction of
Heavily-Obscured AGN
X-ray background
does not constrain
density of heavilyobscured AGN
Direct detections
of individual
sources are
required.
Treister et al. 2009b
How to find distant obscured AGN?
Mid-IR
Most of the absorbed
energy is re-emitted at
IR wavelengths.
Sources with high ratios
of IR (mostly AGN) to
optical (stars) emission
are good candidates to
be obscured AGN.
R-K=2.5log(fK/fR)
Fiore et al. 2008, 2009; Treister et al. 2009
Stacking 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.
- Spectral slope shows a large fraction of heavily obscured AGN
in this sample. Namely, ~90% obscured AGN and 10% starforming galaxies.
Treister et al. ApJ 2009c
X-Ray to Mid-IR Ratio
Both X-rays and
12µm good tracers
of AGN activity.
~100x lower ratio for
X-ray undetected
sources.
Explained by
NH~5x1024 to 1025cm-2
Treister et al. ApJ 2009c
X-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 2009c
Optical/Near-IR SED Fitting
X-ray Undetected
- Median stellar mass
for X-ray detected
sources ~4.6x1011 Msun.
- For X-ray undetected
source ~1011 Msun.
X-ray Detected
Evidence for significant
recent star formation in
most sources
Treister et al. ApJ 2009c
Heavily-Obscured AGN Space Density
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 heavilyobscured phase after
merger?
Treister et al. ApJ 2009c
Obscured to Unobscured Quasar Ratio
IR-selected
Local ULIRGs
Treister et al. submitted
The Merger-Quasar Connection
Obscured quasars are the product of the merger of two
massive gas-rich galaxies. After a time t the quasar
becomes unobscured.
d 2 merger
t
N gal ( M min (z)) f gas(z)
N obsc
dtdN
(z) 
NUnobsc
NUnobsc(z)

Treister et al. submitted
The Merger-Quasar Connection
t=9623 Myrs
The obscured
phase represents
~30% of total
accretion onto
supermassive black
holes
Treister et al. submitted
The Future: NuSTAR
Energy Range
6-80 keV
Angular resolution
40”
Field of View
12’x12’
Flux Limit
~2x10-14 in 1 Msec
Launch Date
August 2011
PI
Fiona Harrison
NuSTAR Observations
NuSTAR will
directly detect a
large number of
heavily-obscured
AGN up to z~1-2.
Summary
• Obscured AGN are critical to understand galaxy
evolution.
• From the Swift and INTEGRAL experiments we are
starting to understand the nearby obscured AGN
population
• Mid-IR selection finds large number of obscured AGN
at larger distances.
• Strong evolution in numbers up to z~3.
• This could be evidence for a heavily obscured phase
after quasar triggering.
• NuSTAR will be critical in understanding the AGNGalaxy connection.