8.971: X-ray Astronomy

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8.971 X-ray Astronomy

• Lecture 12
• Super-Massive Black Holes, Jets, AGN, Quasars,
  Blazars
• Belinda Wilkes
• Chandra X-ray Center
• Smithsonian Astrophysical Observatory

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Super-Massive Black Holes (SMBH)

• Active Galactic Nuclei (AGN)
• Galaxy containing a SMBH (log Mo6-10) at its
  core
• Strong, broad (103 kms-1), high-ionization
  emission lines
• Strong, narrow (100 kms-1), low-ionization lines
• Many observational types, related via Unification
  models
• Quasars/Quasi-Stellar Objects (QSOs)
• Seyfert galaxies (types 1-2)
• Type 1 broad and narrow emission lines
• Type 2 narrow emission lines only
• Broad Line Radio Galaxies
• Narrow Line Radio Galaxies

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X-rays and Active Galaxies

• AGN are multi-wavelength emitters radio-X-ray
  (and ?-ray)
• Strong X-ray sources
• X-ray surveys mostly see AGN so are a good way to
  find them
• Provide information on nuclear regions
• Major advances with current X-ray satellites
• Chandra XMM-Newtons main roles
• Finding new SMBHs Surveys
• High signal-to-noise CCD spectroscopy
• High Resolution Spectroscopy
• X-ray jets

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• Unification

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The Nuclear Regions of an AGN
Nuclear region of an AGN/Quasar

• View of Active Galaxy (AGN) depends on
  inclination
• Optical/UV light obscured when edge-on
• Traditional surveys optical/UV, soft X-ray
• Hard X-ray/IR/radio surveys see all

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Unification Model nuclear regions
Type 1
X-ray reflection off cold/warm material
BROAD LINE REGION
NARROW LINE REGION
Type 2
Scattered, polarized light
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Spectral Energy Distributions of Active Galaxies
Edge-on View
EB-V0.6
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Emission Mechanisms
Radio-quiet
Radio-loud

• Synchrotron
• Synchrotron thermal
• Thermal gas in accretion disk
• Synchrotron self-Compton from radio
• Synchrotron (beamed)

Radio Infrared Optical/UVsoft X-ray Hard
X-ray ?-ray

• Synchrotron
• Thermal dust with wide temperature range
  (50-1000K)
• Thermal gas in accretion disk (AD)
• Thermal Comptonisation of UV

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Complex Unification!

• X-ray surveys generally find
• Type 1 AGN - unobscured
• Type 2 AGN obscured
• Consistent with simple Unification models
• But MANY exceptions
• Broad Absorption Line (BAL)
• Red AGN
• Intermediate types (1.2-1.9)
• XBONGs
• Disk-wind models (Konigl Kartje 1994)

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• Surveys

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To View the Population

• Optical and soft X-rays miss edge-on/obscured AGN
  and quasars
• An unbiased view of the population
• X-ray surveys Chandra, XMM-Newton
• Infrared (IR) Surveys 2MASS, Spitzer
• G-ray Integral
• Low-frequency Radio 3CR
• Many ongoing, deeper, multi-wavelength surveys,
  cover full range of possibly SEDs
• Can Unification explain the many varieties of
  AGN?

20 years ago
Now
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X-ray Surveys

• Strategy layered surveys
• Deep, narrow all populations, small number
  sources, cosmic variance
• Chandra Deep Field North .08 deg2 (1 ACIS-I
  field) 2 Msecs
• Chandra Deep Field South .08 deg2, 2 Msecs
  4 flanking fields, 250 ksecs
• Medium deep, wider larger samples, miss faintest
  AGN, less cosmic variance
• SWIRE 0.6 deg2, 70 ksecs
• COSMOS 0.6 deg2, 200 ksec
• Groth Strip 0.25 deg2, 200 ksecs, 0.25 deg2, 800
  ksec

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X-ray Surveys (cont)

• Layered Surveys (cont)
• Shallow and Wide very large samples, only
  brightest sources, little cosmic variance
• Bootes 9 deg2, 5-10 ksecs
• Multi-wavelength approach, finds more AGN types
• optical (ground based, HST)
• Near-IR (ground-based)
• Far-IR (Spitzer)
• Radio (ground-based)

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SWIRE/Chandra Survey
(w/Lonsdale, Kilgard, Polletta, Smith, Owen, et
al.)

• 0.6 deg2 contiguous, 70 ksecs
• Lockman Hole region of SWIRE
• Centered on Deepest VLA image
• X-ray flux limit 2x10-16 erg cm-2 s-1
• Depth distinction between AGN and starbursts
  (undetected)

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Statistical Results

• 775 unique X-ray sources to a limiting flux of
  2x10-16 erg cm-2 s-1
• 765 with secure IR counterparts and 626 secure
  optical counterparts
• gt160 radio counterparts (analysis on-going)
• 75 spec z (so far)
• 49 X-ray sources coincident with optically
  extended galaxies
• 2 extended X-ray sources (clusters)

SWIRE/Chandra Survey
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SWIRE X-ray Sample

• Standard R vs X plot
• Blue lines indicate AGN region (not well-defined)
• Radio sources all over
• Extended sources in low L AGN region

R
X-ray
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Current X-ray and IR Surveys? Broader range of
SEDs

• Einstein-era optically/radio-selected, blue bias
  (Elvis et al. 1994)
• HEAO hard X-ray, reduces blue bias (Kuraskiewicz
  et al. 2003)
• 2MASS J-Kgt2, red AGN, little/no blue bump
  (Kuraskiewicz et al. 2007, Fig 4b)

IR
Optical
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Obscured AGNlog NH 21-24

• Potential
• Numbers geometry of central regions
• Properties information on obscuring material
• No single population (Alexander et al. 2003,
  Rosati et al. 2002)
• Type 2 AGN/QSOs (Norman et al 2002, Kim et al.
  2006)
• Compton-thick AGN (Polletta et al. 2006)
• XBONGS (Fiore et al. 2000, Kim et al. 2006)
• Obscured type 1 AGN (Wilkes et al 2002)
• Optically Highly Polarized Type 1 AGN
  (Smith et al. 2002)

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Compton-thick AGN
(Polletta et al. 2006)

• 5 hard X-ray selected (2 at zgt2)
• 120 red, AGN-dominated, IR-selected power-law
  SED, aIRgt1.0
• gt25 Compton-thick AGN deg-2
• 40 optical O/IR AGN 60 host galaxy
  dominates
• 30 X-ray detected to F(.3-8)10-15 erg
  cm-2 s-1

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SWIRE X-ray Compton-Thick QSO
(Polletta et al. 2006)

• SW 104409, z2.54
• X-ray HR0.85, 11 cnts
• NLSy1 optical spectrum
• SED
• Obscured QSO, AV4
• 0.6 QSO type 1 (scattered light)

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Red AGN Hard X-ray Spectra

Chandra data Wilkes et al., in prep

• 44 2MASS Red (J-Kgt2) AGN w/Chandra
• 21 spectral fits
• Log NH22
• PL slope flatter for weaker X-rays

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XMM-Newton Observations

(Wilkes, Pounds et al. 2005, 2007)

• 8 X-ray-bright, 2MASS AGN
• Range of optical types and X-ray hardness ratio
• Variety of results
• Complexity in type 1 and 1.5s
• Type 2 consistent with Unification
• Variation in 3 (1 of each type)
• No systematic error in Chandra data
• BUT low S/N data are misleading
• Harder X-ray due to NH reflection

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Complex Red Quasar 2M10495837
Schmidt et al 2007

• Optical Type 1.8
• X-ray hard (HR0.6)
• 2 scattering regions
• Blue thin, small dust grains
• Red dusty region, red due to obscuration
• Starlight dilution
• HST ACS imaging
• Blue fan (3.5
• Red fringe (polar, 2)

Red
Blue
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XMM-Newton Data
Wilkes, Pounds, Schmidt, in prep.

• Unusually hard 2-10keV spectrum, HR0.6
• Requires
• Compton-thick PL
• Unabsorbed Cold Reflection
• Soft excess warm ionized region
• Scattered power law 1.7
  

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Over-the-Top View
Courtesy Charlotte Garcia
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Towards the Full Population

• We are finding a lot of new varieties of AGN
• Collecting so much data on so many sources takes
  a while
• We still do not have a census
• But we will!

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• GRATING SPECTRA

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NGC3783

• Seyfert 1, Redshift, z0.009760, V13.5
• 900 ksec HETG observation (Cycle 2 LP)
• Extremely rich emission and absorption spectrum
• 9 papers modeling physical and dynamical
  conditions and variability
• 3 or 4 co-spatial, out-flowing absorbers, range
  of ionization and velocity
  (Netzer et al 2003, Krongold et al 2003)
• Not many AGN sufficiently bright

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• JETS

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Actual Chandra First Light

• Point Source to focus Quasar PKS0637-75, z0.5
• X-ray Jet visible 10 long, 400,000 lyrs
• Birth of a new research topic!

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M87 Jet in Radio and X-rays
X-ray
Double-lobed radio source with one-sided
relativistic jet
Radio
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X-ray/Radio Jets in Quasars
M87 jet in X-ray, radio and optical
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X-ray Emission Mechanisms

• Radio Synchrotron emission
• Radio/X-ray ratio often constant along 10-100 kpc
  jet length
• X-ray Inverse-Compton (IC) Scattering
• IC Seed photons
• Self, i.e. synchrotron photons
• Cosmic Microwave Background (CMB)
• Ongoing discussion!

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• Double Quasar
• Chandra spatial spectral resolution

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NGC 6240 Galaxy with Double X-ray Core
Starburst LINER z0.0245
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NGC 6240 Spectra
NGC 6240 X-ray Spectrum
Fe Ka (6.4keV)
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2
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NGC 6240 Movie
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X-ray Studies of AGN

• Full View of Population
• from surveys, need Chandra - coming soon!
• Evolution of Population (not today)
• from surveys, need Chandra - very close
• Low-resolution spectral studies
• progress made, XMM-Newton best instrument
• need Con-X to push to high-redshift
• High-resolution spectral studies
• New capability, progress but is hard
• Jets
• New field, lots of progress, Chandra is primary
  instrument