The non-thermal broadband spectral energy distribution of radio galaxies

Gustavo E. RomeroGustavo E. Romero

Instituto Argentino de Radio Astronomía (IAR-CCT La Plata CONICET)Instituto Argentino de Radio Astronomía (IAR-CCT La Plata CONICET)FCAG, Universidad Nacional de La PlataFCAG, Universidad Nacional de La Plata

IAU SED 2011, Preston, UK, 5-9 September, 2011IAU SED 2011, Preston, UK, 5-9 September, 2011Contact: romero@iar-conicet.gov.arContact: romero@iar-conicet.gov.ar

22

AGNs produce gamma-ray emission

The “lepto/hadronic” jet model (in a nutshell)The “lepto/hadronic” jet model (in a nutshell)

Physical conditions near the jet base are Physical conditions near the jet base are similar to those of the corona (e.g. Reynoso similar to those of the corona (e.g. Reynoso et al. 2011; Romero & Vila 2008, 2009; Vila et al. 2011; Romero & Vila 2008, 2009; Vila & Romero 2010) & Romero 2010)

The jet launching region is quite close to the The jet launching region is quite close to the central compact object (few central compact object (few RRgg))

Hot thermal plasma is injected at the base, Hot thermal plasma is injected at the base, equipartition b/w particles and magnetic field equipartition b/w particles and magnetic field to start with.to start with.

Jet plasma accelerates longitudinally due to Jet plasma accelerates longitudinally due to pressure gradients, expands laterally with pressure gradients, expands laterally with sound speed (Bosch-Ramon et al. 2006)sound speed (Bosch-Ramon et al. 2006)

The plasma cools as it moves outward along The plasma cools as it moves outward along the jet. As the plasma accelerates the local the jet. As the plasma accelerates the local magnetic field decreases.magnetic field decreases.

Maitra et al. (2009)

Jet Model – 1. StructureJet Model – 1. Structure

• z0 : base of the jet; ~50 Rg

• zacc < z < zmax: acceleration region; injection of relativistic particles.

• zend : “end” of the radiative jet

• : jet opening angle

• : viewing angle; moderate

z0

zacc

zmax

z

BH

zend

Jet Model – 2. PowerJet Model – 2. Power

z

Edddaccr LqL

12jet jet accrL q L

rel rel jetL q L

rel p e p eL L L L a L

)( exp),(max

zfE

EEzEQ

0.0

0.2

0.4

0.6

0.8

1.0

f (z)

zmax

Content of relativistic particles…

Jet Model – 3. Acceleration and lossesJet 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

• Synchrotron

• Relativistic Bremsstrahlung

• Proton-proton collisions (pp)

1 1( ) <1acct ecB z E 00( ) 1 2

mzB z B m

z

• Inverse Compton (IC or SSC)

• Proton-photon collisions (p)

• Adiabatic cooling

Jet Model – 4. Particle distributionsJet Model – 4. Particle distributions

Calculation of particle distributions: injection, cooling, decay, and convection

Also for secondary particles: charged pions, muons and electron-positron pairs

p p e e

( ) op p a b e ee

( ) op p p a b

• Direct pair production

• Photomeson production & pp collisions

e e

Interaction of relativistic p and e- with

magnetic field

radiation fields

in the jet

, , p e B p e e e

( ) op p a b 2o

p p e e

• Synchrotron radiation* Inverse Compton (IC)

•Relativistic Bremsstrhalung

• Photohadronic interactions (p)

v e ee

e B e

( ) op n a b

• Proton-proton inelastic collisions p + p p + p + a 0+ b(+ +-)

Radiative processes in jets Radiative processes in jets ((e.g. e.g. Romero & Vila 2008, Vila & Romero & Vila 2008, Vila & Aharonian 2009, Aharonian 2009, Vila & Romero 2010))

matter

IC Cascades

Ore

llana

et a

l. (2

007)

• Disc• Corona• Jet synchr. (SSC)

• Photon energy densities > magnetic energy density

See Bednarek’s many papers on the topic. Also Pellizza et al. 2010, and Bosch-Ramon & Khangulyan 2009 review.

Absorption

Absorption in matter Photon-photon absorption

Example: Cen A

Lj~6 x1044 erg/sMbh~ 108 Mʘ

Losses (from Reynoso et al. 2011)

Absorption

SED

Example: M87

Lj~2 x1046 erg/sMbh~ 6 x 109 Mʘ

Losses (from Reynoso et al. 2011)

Absorption

SED

Powerful blazars - Variability

PKS 2155-304

Powerful blazars – Variability…radio/optical

Romero et al. (1994, 2000a, b)

PKS 0537-441

Two-fluid jet model (Sol et al. 1989, Romero 1995, Reynoso et al. 2011)

BB

black hole jet

disk wind

- – magnetic flux accumulated by the BH

A highly relativistic pair jet is driven by the ergosphere and the barion loaded jet is produced by the disk.

Sol et al. (1989); Romero (1995, 1996); Roland et al. (2009)

Two-fluid jet model

Romero (1995, 1996)

Kelvin-Helmholtz instabilities develop in the interface between both fluids.

The axial magnetic field will prevent the development of inestabilities if larger than Bc

given by:

Moll (2010)

2525

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).

Rapid variabilityRapid variability

Extreme TeV blazars

The variability follows the inhomogenous structure of the beam, with regions of different photon field density (Qian et al. 1991, Romero et al 1995)

Variability timescale; l is the linear size of the inhomegeneities. For l~1014-15 cm → tv~1-10 min

Changes in the optical polarization (Andruchow et al. 2005)

An application to a Galactic source – An application to a Galactic source –

Fit to the spectrum of the LMMQ XTE J1118+480Fit to the spectrum of the LMMQ XTE J1118+480

-5 0 5 10 1528

29

30

31

32

33

34

35

36

37

Log10(E /eV)

Log 10

(L /

erg

s-1)

discsynchrotronSSCppp

Fermi

VERITASCTA

• zacc = 6x108 cm zmax = 10 zacc

• zend = 1012 cm

• B(z) = K z-1.5

• = 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

2005 outburst

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.

Thank you!

Cen A

M 87

Evolution of the bulk Lorentz factor