RH and MHD models for AGN jet propagation and deceleration

19 Pages·2010·1.89 MB·English

by  Rony Keppens

Relativistic HD and MHD models for
AGN jet propagation and deceleration
Rony Keppens
CentreforPlasmaAstrophysics,K.U.Leuven
FOM-InstituteforPlasmaPhysicsRijnhuizen
AstronomicalInstitute,UtrechtUniversity
COST Action MP0905, WG Meeting Bonn, 24 June 2010
In collaboration with:
• Z.Meliani
RonyKeppens AGNjetmodeling
Outline
• Fanaroff-Riley classification and HYMORS
⇒ contemporary challenges in AGN jet modeling
• Relativistic(M)HDsimulations
⇒ relativistic HD jet simulations and HYMORS
⇒ relativistic (M)HD two-component jet simulations
• Outlook
RonyKeppens AGNjetmodeling
Fanaroff-Riley 1974 classification
• correlation radioluminosity - positions high-low surface brightness
⇒ Class I – Class II transition: at well-defined L
178Mhz
• FR I: brightest near core, jets in 80 %, relativisticatparsecscalewhile
diffuseandsubrelativisticatkpc
3C31
• FR II: emission in lobesandhotspots; narrow, highly relativistic jet
CygnusA
• relation radio appearance - IGMenergytransport/deposition
RonyKeppens AGNjetmodeling
HYMORS
• Gopal-Krishna & Wiita 2002: Hybrid Morphology Radio Sources
⇒ FR I appearance on one side, FR II characteristics
⇒ FR I/II classification relates to ambientmediumdifferences
NGC612
⇒ FR II lobe with hotspot to SE, diffuse jet to NW (FR I)
⇒ source yields ‘identical’ launch conditions at each side
RonyKeppens AGNjetmodeling
AGN jet challenges
• How to decelerate highly energetic (especially FR II) flows?
⇒ HYMORS suggest externalmediuminfluence, study with
axisymmetric HD jet models
• jet launch models and observations point out transversestratification
⇒ source region controls inner/outer jet properties
⇒ FR II/FR I transition: liabilitytorelativisticRayleigh-Taylormode
⇒ relativistic 2.5D and 3D (M)HD simulations
• Magnetization of jet flows
⇒ roleofhelicalB incollimation/propagation
RonyKeppens AGNjetmodeling
Model parameters
• jet kinetic energy & Lorentz factor Γ (order 10-20)
• ratio between jet/IGM inertia (density contrast)
• opening angle: cylindrical/conical models
poloidal plane
θ contact discontinuity higher density
symmetry medium
conical jet
• external medium stratification: include densitydiscontinuities
⇒ inevitable boundaries seperating differing regions of influence
• specialrelativistic(magneto)hydro equations
RonyKeppens AGNjetmodeling
• Relativisticallycorrectidealgas: effectiveγ(T)
⇒ varying polytropic index: affects compression rate, shock strength
• Application: AGNjetsencounteringdensitydiscontinuity
⇒ simulatejetpropagationthroughlayeredmedia
⇒ Γ ’ 20 beam Lorentz factor, L ∼ 1046ergs/s.
Jet,Kin
• lower region: lighter medium ρ /ρ = 0.1496
Low b
⇒ after 160 light crossings zoomonjetheadbeforejumpencounter
• preformedjethead: ultrarelativisticstateinshocked,swept-upISM
⇒ effect on dynamics as it penetrates denser region
RonyKeppens AGNjetmodeling
• explored differences between low-highenergyjets: 1043 or1046ergs/s
⇒ jet beam kinetic luminosity
L = (Γ h −1)ρ Γ πR2v
jet,Kin b b b b b b
⇒ 10 model computations, varyingΓb = 10−20andθ = 0−1
⇒ always CD, with/out ρ variation, Case II 1046ergs/s at t = 900
⇒ FRIIjetatfirst,thendramaticslowdownwithFRIappearance
RonyKeppens AGNjetmodeling
• high energy jets: need significant contrast to induce FR I transition
⇒ Γ = 10, densityjump10-1000, IGM stratification effects
RonyKeppens AGNjetmodeling
A&A 491, 321-337 (2008)
• overall findings on jet deceleration
⇒ FRII-FRItransitionfeasibleatlargedensitycontrast
⇒ FR I changeover: relativistic at pc to subrelativistic at kpc
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RonyKeppens AGNjetmodeling