Diapositiva 1

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The non-thermal broadband spectral energy
distribution of radio galaxies
Gustavo E. Romero Instituto Argentino de Radio
Astronomía (IAR-CCT La Plata CONICET) FCAG,
Universidad Nacional de La Plata
IAU SED 2011, Preston, UK, 5-9 September,
2011 Contact romero_at_iar-conicet.gov.ar
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AGNs produce gamma-ray emission
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The lepto/hadronic jet model (in a nutshell)

• Physical conditions near the jet base are similar
  to those of the corona (e.g. Reynoso et al. 2011
  Romero Vila 2008, 2009 Vila Romero 2010)
• The jet launching region is quite close to the
  central compact object (few Rg)
• Hot thermal plasma is injected at the base,
  equipartition b/w particles and magnetic field to
  start with.
• Jet plasma accelerates longitudinally due to
  pressure gradients, expands laterally with sound
  speed (Bosch-Ramon et al. 2006)
• The plasma cools as it moves outward along the
  jet. As the plasma accelerates the local magnetic
  field decreases.

Maitra et al. (2009)
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Jet Model 1. Structure

• z0 base of the jet 50 Rg

• zacc lt z lt zmax acceleration region injection
  of relativistic particles.

• zend end of the radiative jet

• j jet opening angle

• q viewing angle moderate

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Jet Model 2. Power
Content of relativistic particles
z
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Jet Model 3. Acceleration and losses
Maximum energy determined by balance of cooling
and acceleration rates

• Acceleration diffusive shock acceleration

• Cooling processes interaction with magnetic
  field, photon field and matter

• Inverse Compton (IC or SSC)
• Proton-photon collisions (pg)
• Adiabatic cooling

• Synchrotron
• Relativistic Bremsstrahlung
• Proton-proton collisions (pp)

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Jet Model 4. Particle distributions
Calculation of particle distributions injection,
cooling, decay, and convection
Also for secondary particles charged pions,
muons and electron-positron pairs

• Direct pair production

• Photomeson production pp collisions

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Non-thermal radiative processes in jets

• Relativistic particles electrons, protons,
  secondary particles (m, p, e)

• Target fields magnetic fields, radiation
  fields, matter fields

• Acceleration mechanism

• Diffusive shock acceleration

• Converter mechanism,

• Target fields

• Internal locally generated photon fields,
• magnetic field, comoving
  matter field

• External depending on the context

• stellar winds and photons,
• accretion disc photons,
• clumps, clouds, ISM

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Radiative processes in jets (e.g. Romero Vila
2008, Vila Aharonian 2009, Vila Romero 2010)
magnetic field
Interaction of relativistic p and e- with
in the jet
matter
radiation fields

• Synchrotron radiation

• Inverse Compton (IC)
• Relativistic Bremsstrhalung

p p ? p p a ?0 b(? ?-)

• Proton-proton inelastic collisions

• Photohadronic interactions (pg)

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See Bednareks many papers on the topic. Also
Pellizza et al. 2010, and Bosch-Ramon
Khangulyan 2009 review.
IC Cascades

• Photon energy densities gt magnetic energy density

• Disc
• Corona
• Jet synchr. (SSC)

Orellana et al. (2007)
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Absorption
Absorption in matter
Photon-photon absorption
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Example Cen A
Lj6 x1044 erg/s Mbh 108 M?
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Losses (from Reynoso et al. 2011)
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Absorption
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SED
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Example M87
Lj2 x1046 erg/s Mbh 6 x 109 M?
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Losses (from Reynoso et al. 2011)
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Absorption
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SED
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Powerful blazars - Variability
PKS 2155-304
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Powerful blazars Variabilityradio/optical
PKS 0537-441
Romero et al. (1994, 2000a, b)
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Two-fluid jet model (Sol et al. 1989, Romero
1995, Reynoso et al. 2011)
B
B
black hole jet
A highly relativistic pair jet is driven by the
ergosphere and the barion loaded jet is produced
by the disk.
Y
disk wind
- Y magnetic flux accumulated by the BH
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Two-fluid jet model
Sol et al. (1989) Romero (1995, 1996) Roland et
al. (2009)
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Moll (2010)
The axial magnetic field will prevent the
development of inestabilities if larger than
Bc given by
Kelvin-Helmholtz instabilities develop in the
interface between both fluids.
Romero (1995, 1996)
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Shocks develop when the magnetic energy decreases
and charged particles are re-accelerated by a
Fermi-like mechanism (alternatives converter
mechanism Derishev , local magnetic
reconnection Lyubarsky). Power-law populations
of non-thermal particles are injected. These
particles will interact with the local
inhomogeneities, producing variable non-thermal
radiation (Marscher 1992, Romero 1995).
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Rapid variability
Extreme TeV blazars
Variability timescale l is the linear size of
the inhomegeneities. For l1014-15 cm ? tv1-10
min
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Changes in the optical polarization (Andruchow et
al. 2005)
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An application to a Galactic source
Fit to the spectrum of the LMMQ XTE J1118480
2005 outburst

• zacc 6x108 cm zmax 10 zacc
• zend 1012 cm
• B(z) K z-1.5
• h 0.01
• Laccr 0.1 LEdd Ljet 5x1036 erg s-1
• Lrel 0.1 Ljet Lp 5 Le 5x1035 erg s-1
• Emin 50 mc2 Q K E-1.5

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Conclusions

• Barion loaded jets with particle injection
  along inhomogeneous regions can explain the
  non-thermal spectral energy distribution of AGNs.
• Electron-positron beams moving inside the
  hadronic jets can play a role in the generation
  of non-thermal rapid variability.
• The fine resolution in HE SED and the rapid
  variability obtained with the future CTA
  Observatory can be used to constrain this tipe of
  models and the location of the emission region in
  the sources.

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Thank you!
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Cen A
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M 87
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Evolution of the bulk Lorentz factor