Structure of jet cores in blazars: g-ray observations

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Structure of jet cores in blazars g-ray
observations
Greg Madejski Stanford Linear Accelerator Center
and Kavli Institute for Particle Astrophysics
and Cosmology

• In collaboration with Jun Kataoka, Tad
  Takahashi, Marek Sikora, Rie Sato,
• Lukasz Stawarz, Masayoshi Ushio, others
• Context blazars as active galaxies with
  dominant relativistic jet
• Main questions structure, acceleration,
  collimation, and content of the jet,
• -gt all inferred from radiative processes via
  broad-band spectra
• Recent Suzaku observations of blazars
• signature of bulk-Compton process in PKS
  1510-089?
• X-ray spectral shape of Mkn 421 distribution
  of radiating electrons
• Future GLAST

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Mkn 421 data from Macomb et al. 1995
Context extragalactic jets and their g-ray
emission
X-ray variability of Mkn 421 (Takahashi et al.
1996)

• Jets are powered by accretion onto a massive
  black hole the details of the energy conversion
  process
• are still poorly known but g-rays often
  energetically dominant blazar phenomenon
• Gamma-ray emission often extends to the TeV
  region
• All inferences hinge on the current standard
  model broad-band radiation is due to
• the synchrotron inverse Compton processes
• We gradually are developing a better picture of
  the jet (content, location of the energy
  dissipation), but
• how are the particles accelerated? Where?
  Protons or electrons? are still open questions
• Variability (simultaneous broad-band monitoring)
  can provide crucial information about the
  structure and
• content of the innermost jet, relative power as
  compared to that dissipated via accretion,

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Another example archetypal GeV blazar 3C279, 96
flare
Data from Wehrle et al. 1998

• Correlated variability on day time scales is
  common
• Variable emission presumably arises in the
  innermost regions of the jet (but this is
  arguable)
• Variability in X-ray and g-ray bands puts
  constraints on the minimum relativistic boost
  (Gj) of the innermost region (via g-g absorption
  to e/e- pair production)
• Lorentz factors Gj of jets inferred from VLBI
  (multi-parsec scales) can be compared against Gj
  inferred from variability (sub-parsec scales)
• -gt Gj as a function of distance from the black
  hole? - gt constraints on acceleration process of
  the jet

Data from Jorstad et al. 2000
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Suzaku observations of PKS 1510-089 hard power
law soft excess

• Suzaku observed a number of blazars - the list
  includes many detected by EGRET and TeV
  observatories
• Generally, the X-ray spectra of EGRET blazars are
  very hard power laws (energy indices often lt
  0.5), extending into the HXD PIN energy range
  (contrast to TeV blazars)
• Very difficult to explain such hard spectra!
• Interesting recent result is for PKS 1510-089, a
  blazar at z 0.3 for 120 ks (joint observation
  of Jun Kataoka GM Kataoka 2008)
• Spectrum is a hard power law (energy index a
  0.2), but with a soft X-ray excess below 1.5
  keV, best described as a steep power law or a
  thermal component with kT 0.2 keV
• Explanation as a tail of the synchrotron
  emission unlikely extrapolation does not work
• Too hot to be the tail of the blue bump

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Suzaku observations of PKS 1510-089 possible
evidence for bulk-Compton bump -gt constraints
on the jet content?

• This soft excess might be the tentative evidence
  for the Sikora bump arising by the inverse
  Compton scattering of BEL light by the cold
  electrons comoving in the relativistic jet
  (Ebump E(Lya) x G2 1 keV)
• Even if it is not bulk-Compton
• From its isotropic luminosity of LBC lt 3 x 1044
  erg/s - we can set a limit on the energy flux
  Le,cold carried by the cold electrons and the
  e/e- pair content of the jet

• since LBC (4sT/3mec2) UBEL rBLR Gj3 Le,cold
• we have
• Le,cold
• lt 2.7x1043 (rBLR/0.1pc) (Gj/10)-3
  (LBEL/1045erg/s)-1 erg/s
• Significantly less than the required kinetic
  luminosity of the jet
• Now the total power delivered by the jet
• must be 8x1044 erg/s
• With more realistic parameters, ne/np in the jet
  is lt 5
• -gt Jet contains more pairs than protons, but
  cannot be
• dynamically dominated by e/e- pairs
• For details, see Kataoka 2008

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Another recent example Mkn 421 observed with
Suzaku
Mrk 421
Ushio, GM, 08 in preparation

• Broad-band X-ray spectrum measured by Suzaku
  cannot be described as a simple power law
• Instead, the index steepens with increasing
  energy
• Assuming constant B field, steepening electron
  distribution is implied
• Best fitted with power-law electron distribution
  (index 2.2), with super-exponential cutoff
• (as inferred for some SNR Tanaka et al. 2008)
• Such a cutoff is predicted in, e.g., radiating
  relativistic electrons that were accelerated in
  turbulent B field
• (see, e.g., Stawarz and Petrosian 2008)
• Applicable to many blazars where the X-ray band
  represents the high-energy tail of the
  synchrotron peak
• (often the TeV blazars)

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EGRET All Sky Map (gt100 MeV) precursor to GLAST
3C279
Cygnus Region
Vela
Geminga
Crab
PKS 0528134
LMC
Cosmic Ray Interactions With ISM
PKS 0208-512
PSR B1706-44
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Rocket Fairing installation around GLAST
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GLAST Launch

• Launch from Cape Canaveral Air Station 11 June
  2008 at 1605PM UTC
• Circular orbit, 565 km altitude (96 min period),
  25.6 deg inclination.
• Communications
• Science data link via TDRSS

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GLAST is in orbit!

• Schematic principle of operation
• of the GLAST Large Area Telescope
• g-rays interact with the hi-z material in the
  foils, pair-produce,
• and are tracked with silicon strip detectors
• The instrument looks simultaneously into 2
  steradians of the sky
• Energy range is 0.03-300 GeV, with the peak
  effective area of 12,000 cm2 - allows an
  overlap with TeV observatories
• Why SLAC? clear synergy with particle
  physics
• - particle-detector-like tracker/calorimeter
• - potential of discovery of dark matter
  particle

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• GLAST observing strategy performance angular
  resolution, broad-band sensitivity (1 year)

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Engineering Data Single Events in the LAT

• The green crosses show the detected
  positions of the charged particles, the blue
  lines show the reconstructed track trajectories,
  and the yellow line shows the candidate gamma-ray
  estimated direction.  The red crosses show the
  detected energy depositions in the calorimeter.  

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GLAST LAT has much higher sensitivity to weak
sources, with much better angular resolution
GLAST
EGRET
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Example of flaring activity of blazarsRecent
outburst of 3C454.3
Objects subject to intensive monitoring (GLAST
LAT g-ray flux history will be available, no
special repointing)
3C273 NRAO 530 3C279 1ES195965 PKS 0528134 OJ
287 3C454.3 0716714 PKS 1510-089 PKS
2155-304 Mkn 421 PKS 0208-512 BL
Lacertae 0836714 PKS1622-297 Mkn
501 1406-076 1426428 W Com (1219285) http/gla
st.gsfc.nasa.gov/ssc/data/policy
GLAST flux limit for reporting of major
flares 2 x 10-6 photons/cm2/s (Egt100 MeV)
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• Clusters of galaxies with GLAST and NuSTAR

From Markevitch et al. (X-ray data 2004, 2005)
Clowe et al. NuSTAR schematic SMEX (lensing
data 2004), and Bradac et al. 2006 (SW
lensing) sensitive hard X-ray (10-80
keV) telescope system launch
2011-2012 What are details of formaton of
clusters? Non-thermal processes? Jet-cluster
interaction? Best studied in hard X-rays or
g-rays inverse Compton of CMB or thermal X-ray
photons against clusters relativistic particles