Multi - emission from large-scale jets Fabrizio Tavecchio INAF – Osservatorio Astronomico di Brera

Outline Introduction X-rays from radiogalaxies: synchrotron from HE electrons X-ray jets in QSO: the IC/CMB model Recent observations Criticisms, alternatives

Almost every galaxy hosts a BH 99 % are silent 1 % are active 0.1% have jets

Cygnus A Relativistic jets: channels transporting MassMomentumEnergy from the central BH to the IGM core Hot spots lobes

The unification scheme: radiogalaxy, RL QSOs blazar

Jets: from the BH to large scale Resolved X-ray jet Blazar emission region Accretion region VLBI region

X-rays: a new window on old problems Acceleration and collimation Power, composition Particle acceleration …

Siemiginowska et al PKS Chartas et al Cen A Hardcastle et al Pic A Wilson et al. 2000

Producing X-rays in large-scale jets Powerful (aligned) QSOs IC/CMB Tavecchio et al Celotti et al Synchrotron SSC thermal Schwartz et al very energetic electrons Radiogalaxies FRIs: Synchrotron e.g Worrall et al. 2001, 2002 FRIIs: Synch? SSC? e.g Wilson et al. 2001

Pesce et al C371: a synchrotron jet Knot B Knot A  e ~10 7

X-rays radiooptical M87

Very high-energy electrons (  e ~10 7 ) injected in-situ within the jet (shocks? reconnection?) Radiogalaxies (FRI):

Powerful QSOs

Synchrotron IC/CMB  at >100 kpc 

Amplification of the CMB energy density  =10 Photons will appear more concentrated in time and with an energy    U’~U  2

 =10 L’=1 L=160,000 L= L=3x Amplification of the emission  = [  (1-  cos  )] -1

Parameter space Equipartition (radio) IC with CMB (radio and X-rays) small  ~5 deg  ~10  ~10

A Chandra-HST survey of jets 17 “radio selected” jets 10 with X-rays (59%) 10 with optical Sambruna et al Sambruna et al IC/CMB knots

Deep images

Synchrotron to Compton transition?

Speed and power The model allows us to constrain the physical parameters of jets at kpc scale  ~3-10 P~ erg/s Supported by recent numerical simulations (Scheck et al. 2002), but see Wardle & Aaron 1997 Fast spine? (Chiaberge et al. 2000; Celotti et al. 2001)

Problems, criticisms, alternatives Cooling: why X-ray knots? Large power requirements (~10 48 erg/s) Close alignement (small prob.)

Clumps in jets? cannot cool Problem: the X-ray emitting electrons cannot cool inside the knot even including adiabatic losses! Tavecchio, Ghisellini & Celotti 2003

A possible solution Several compact regions overpressured with respect to the external plasma (instabilities, clouds, entrained material, reconnection sites) Consequence: expected variability in knots (~month) expansion very efficient adiabatic losses

New evidences: Several knots in M87 are variable! (Harris et al. 2003) Cen A shows compact X-ray/radio knots (Hardcastle et al. 2003)

Synchrotron from complex electron distributions: Alternatives to the IC/CMB:

Dermer & Atoyan 2002  ~ cooled electrons uncooled electrons From cooling…

…or from acceleration Multiple shocks or turbulence (Stawarz et al. 2004): Marcovith & Kirk 1999

Synchrotron from another electron component or from HE protons… Aharonian 2002

Secondary electrons could be produced through p-  or p-p inefficient, Urad quite small a density of ~1 part/cm 3 is necessary Aharonian 2002

Summary The IC/CMB model works well for powerful jets in QSO Deep pointings reveal synchrotron to IC transition along the jet Radiogalaxies: a unique synchrotron component from radio to X-rays – acceleration mechanism? BUT: problems with low E electrons: clumps? More observations and exploration of alternatives…

From subpc to kpc-scale Blazars and Chandra: physical quantities at (very) different scales! Example: (z=0.361) B=2G; R=3x10 cm 16 B=0.6x10 G; R=2x10 cm -522

Problems, criticisms, alternatives Cooling: how to produce X-ray knots? Large power requirements (~10 48 erg/s) Close alignement (small prob.) Global behaviour (but see G&K 2003) {

Layer and spine

M87

PKS Siemiginowska et al Offsets?

Evidences for small angles from superluminal motions: Lorentz factor Angle