Relativistic Jets, Ann Arbor 2005 The two-flow model : a unifying paradigm for AGNs and microquasars relativistic jets. G. Henri Laboratoire d ’Astrophysique de Grenoble, France Coll: G.Pelletier, J. Ferreira, P.O. Petrucci Students : A. Marcowith, N. Renaud, L. Saugé, T.Boutelier
Relativistic Jets, Ann Arbor 2005 Why are relativistic jets difficult to produce? Require a very high magnetization or thermal enthalpy (very low baryon load < b -1 ) : must be assumed a priori (very far from equipartition). Difficult to collimate : relativistic E field decollimates the jet (but see Vlahakis & Königl ‘04 ?). Subject to Compton Drag, especially for light e - -e + jets.
Relativistic Jets, Ann Arbor 2005 Evidence for different ejection velocities Relativistic ejections during flares : superluminal velocities (Mirabel Rodriguez ‘94) Compact jets observed during low-hard « plateau » states Brightness contrast implies ~ 0.1 to 0.5 (Dhawan ‘00) GRS AGN e.g (Hummel et al. 1992) Two-sided kpc scale One sided pc scale superluminal motion, vapp = 6 c Either is varying by ~ 50° Or b is varying from 7 to 1.08….
Relativistic Jets, Ann Arbor 2005 The « Two flow » model Two flow model : 2 distinct flows (Sol, Pelletier, Asséo ‘85, H. & Pelletier ‘91), introduced first for explaining radio observations. MHD jet e - p+ mildly relativistic *carries most of the power *fuelled by accretion disk *large scale structures, hotspots Ultra relativistic e + -e - pair plasma * Generated in the « empty » funnel, no baryon load. * Produces high energy photons and relativistic motions * Energetically minor component +
Relativistic Jets, Ann Arbor 2005 The « slow » MHD component Baryonic jet can be emitted from the accretion disk through MHD mechanism ( a la Blandford-Payne) (Ferreira et al., ‘97, ‘04) B field extract angular momentum and power from the JED (Jet Emitting Disk) Disk weakly radiative (mimic ADAF) Jet only mildly relativistic under self consistent accretion- ejection conditions =p B /(p g +p rad ) ~ 0.1 to 1 NB :curvature of B field lines can be achieved because v r /v Kepl =h/r (SS : v r /v Kepl =(h/r) 2 )
Relativistic Jets, Ann Arbor 2005 Formation of the « fast » pair plasma In situ generation of pair plasma in the MHD funnel (H.& Pelletier 91, Marcowith et al. ‘95) Produced through gamma-ray emission Injection of some relativistic particles X-ray and gamma-ray emission by IC and/or SSC annihilation forms new pairs Continuous reacceleration by MHD turbulence necessary for a pair runaway to develop. Limited by the free energy available: saturation must occur at some point.
Relativistic Jets, Ann Arbor 2005 What is the effect of « Compton Drag » ? Common wisdom :Inverse Compton process tends to slow relativistic jets But Anisotropic Inverse Compton acts more like an « automatic pilot» ! Sets up an « equilibrium » Lorentz factor for which the aberrated net flux vanishes On the axis of a standard accretion disk eq ~ (z/Ri) 1/4 predicts progressive acceleration along the axis, but rather inefficient for a single particle (cold plasma) Cold plasma b∞ ~ l s 1/7 ~ 3 z/rg bb
Relativistic Jets, Ann Arbor 2005 Getting relativistic: Bulk acceleration of rekativistic pair plasma Efficiency of radiative acceleration much higher for hot relativistic plasma (Compton « rocket » effect, O’Dell ‘81) but requires continuous reacceleration.,only possible with an external energy reservoir : surroundig MHD jet Precise calculations : maximum efficiency limited by Klein-Nishina cut-off : Lower value for µ-quasars than for AGNs (Renaud & H. ‘98) S=1.5 S=2 S=2.5 S=3 bb S=1.5 S=2 S=2.5 S=3 M = 10 8 Msol M = 10 Msol Cold plasma Hot plasma b∞ ~ l s 1/7 ~ 3 b∞ ~ (l s / ) 1/7 ~ 10
Relativistic Jets, Ann Arbor 2005 Application to microquasars We propose to interpret the various canonical states of X-ray binaries and µ quasars in the frame of the 2-flow model (Ferreira ‘06) Subrelativistic compact jet Superluminal ejections, pairs produced by the non- thermal power-law Quiescent Low-hard Very High Intermediate Thermal soft
Relativistic Jets, Ann Arbor 2005 Application to AGN spectra : a complete spectral fit of 3C279 data.
Relativistic Jets, Ann Arbor 2005 Some words about variability Transition radius can be located at large distance (but non radiative JED does exist inside) : LF QPO associated with the jet/corona. Pair production naturally explosive : quenching mechanism when tapping the energy from the surrounding jet (Saugé, PhD 2004) Energy reservoir Photons Pairs acceleration Pair creation Radiative cooling Luminosity Constant injection
Relativistic Jets, Ann Arbor 2005 The « Doppler factor crisis » of TeV blazars In most TeV blazars, transparency arguments require high Doppler factor ~ 50 in all « one zone SSC » models. But other arguments indicates much lower values Absence of high superluminal motions Low brightness temperatures Detection of unbeamed radio-galaxies in -rays Cen A (EGRET), M87 (HEGRA, HESS) Unification models BL Lacs-FRI Luminosity ratio Number of sources Converge all to ~3 - 5 Fast spine in jet solves some problems but not all !
Relativistic Jets, Ann Arbor 2005 A clue to the issue : inhomogeneous jet transparency implies an upper limit on local soft photon density, depending on Assuming = 3 implies * inhomogeneous emission zone (stratified jet ) * Local monoenergetic or quasi- maxwellian distribution Moderately high Homogeneous models require ~50 All of these being natural outcomes of two-flow model. H. & Saugé ‘06 =1
Relativistic Jets, Ann Arbor 2005 Summary 2-flow model can account for most observational and theoretical constraints of relativistic jets Requires only powerful subrelativistic jet and non thermal acceleration process (which are required anyway): generate self consistently a relativistic pair plasma. Can account for superluminal motion, radiative processes and variability Time dependant, realistic 3D simulations under work to compare with observations (HESS, quasars)