Post on 27-Mar-2015
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SIMULATIONS OF SIMULATIONS OF
ASTROPHYSICAL JETSASTROPHYSICAL JETS
Gianluigi Bodo, Claudio Zanni, Attilio Ferrari, Gianluigi Bodo, Claudio Zanni, Attilio Ferrari, Silvano Massaglia, A. Mignone, P. RossiSilvano Massaglia, A. Mignone, P. Rossi
INAF - Osservatorio Astronomico di TorinoINAF - Osservatorio Astronomico di Torino
Università di Torino Università di Torino
Collimated, supersonic outflows (jets)are generated in many astrophysicalenvironments
AGN
YSOX-ray transients
pulsars
Wide range of scales and velocities
Scales from below the pc up to Mpc
Highly relativistic velocities (AGN, GRB)
Mildly relativistic velocities (X-ray transients – galactic superluminals, SS433)
Few hundreds km/s (YSO)
YSO jets HST images HH 30
1"10''
AGN Jets
Scales up to MpcNon-thermal synchrotron radiationCollimation angle can be few degrees
Observed at differentenergies
time scales 10 yrs7
• Launching Launching phase: acceleration fromdisk and collimation• Propagation Propagation phase: confinement,stability, entrainment• Termination Termination: interaction with external medium
BASIC PROBLEMS
THE TOOL: PLUTO OUTLINE• Explicit, compressible code (FV):
– Shock capturing– High-mach number flows
• Works in 1, 2, 3-D• Modular structure:
– Physics– Time stepping– Interpolations– Riemann Solvers
• HD, MHD, RHD (Mignone, Plewa, Bodo 2005, HLLC Mignone & Bodo 2005) , RMHD (HLLC Mignone & Bodo 2005)
• Geometry support (Cart, Cyl, Spher)• Radiative losses
Algorithms
Time Stepping
Fwd Euler (Split/Unsplit) RK 2nd (Split/Unsplit) RK 3rd (Split/Unsplit) Hancock (Split/CTU) Characteristic Tracing
(Split/CTU)
Interpolation Prim. TVD-limited (II order) Characteristic TVD-limited Piecewise-Parabolic Multi-D Linear Interpolation 2nd and 3rd order WENO
Riemann Solvers Riemann (non-linear)
TVD/ROE HLL HLLC TVDLF
(split) (split)
HD RHD MHD RMHD
Stability of jets
Kelvin-Helmholtz instability
Transfer of momentum, entrainment
Effects on the jet evolution
Consider first a simple case, simple planar shearlayer
Velocity profileVx = tanh y
AGN: relativistic case
Linear stability: different regimes depending on the Mach number, monotonic instability at low Mach, overstability at high Mach
Nonlinear evolution dominated by vortices or by waves
Layer width velocity Layer width tracer
Relativistic cases: correspondence at equal Mr = v/s cs
we showed in linear analysis (Bodo, Mignone & Rosner 2004)that the stability limits (vortex sheet) are the same if expressed in Mr
We introduced a tracer passively advected to distinguish the material on the two sides
JET STABILITYJET STABILITY
Linear phase
Acousticphase
Mixingphase
Bodo et al. 1998
Fanaroff-Riley classificationFanaroff-Riley classification
FR II or lobe dominated “classical doubles”
FR I or jet dominated
Cygnus AVLA
3C 449VLA
Jet velocitiesNo direct velocity measures Evidences for relativistic motions on pc scale come from:
Superluminal motions
Jet one-sidedness
Rapid variabilities
High brightness temperatures
In FRI radiosources jets on kpc scale become symmetric
Brightness ratio between jetand counterjet in 3C31
3C272.1
VLBI one-sided jet VLA
AGN jets: deceleration of FRI jets
Mass entrainment
Injection from stellar winds (Komissarov 1994; Bowman, Leahy, Komissarov 1996)
Entrainment through the instability evolution
Simulations of a propagating jet perturbedat the inlet
Physical parameters
j j
e
Jet Mach number
Lorentz factor
Density ratio
Mach 3, 30Density ratio (lab frame) 10 1000Lorentz factor 10
Low resolution 12 points over radiusHigh resolution 25 points over radius
Stretched grid in the transverse directionIncreasing grid size
Parameters values
3D Numerical Simulation 3D Numerical Simulation
Grid: 300x800x300
Jet injection+perturbation
outflow
outflow
outflow
1) M=3 =1000 =10 t=760
1)
The entrainment is mediated by the cocoon
M=30 =10 =10 t=265
1)
2)
1) M=3 =1000 =10 t=760
2) M=30 =10 =10 t=265
Faster decelerationStrong pinching due to high pressure cocoonShort wavelength mode more efficient for entrainment
Helical mode
Jet mass External mass
Jet mass
External mass
Jet-IGM interaction from the point of view of IGM
Observational consequences of the interaction: X-ray observations
From the observations can we deduce information on jet parameters?
Heating of IGM
CHANDRA
HYDRA A X-RAY
HYDRA AX - RADIO
CHANDRA
Perseus AX - radio
Perseus A X-ray
OBSERVATIONS
X-ray cavities corresponding to radio lobes Shells surrounding the cavities Shell temperature equal or lower than the surrounding medium
Weak shocks
L-T relation for cluster gas
NUMERICAL SIMULATIONS
reflecting
outflow
outflow
refl
ecti
ng
0 2.6
2.6Initial density distribution
Uniform temperature
1024x1024 grid points
Jet inlet
UNITS
RESULTS
M
Subsonic jet lc = 0.5
lc = 1lc = 2
Strongly overpressured
Weakly overpressured
Similar setup as before
Larger grid, Longer integration times,longer than the lifetime of the radiosource
Three cases withcluster of different scales:
T 0.5 keV 1 keV 2 keV
Entropy and dissipated energyEntropy and dissipated energy
Efficiency Efficiency Borgani et al. (2002)Borgani et al. (2002)
Hydrostatic equilibriumHydrostatic equilibrium
Lloyd-Davies et al. (2000)Lloyd-Davies et al. (2000)
L-T relationL-T relation
Entropy per particleEntropy per particle(at )(at )
First stage, future: insert heatingat z > 0 on protoclusters and follow the evolution with a cosmological simulation
Summary
Single shear KH instability
Deceleration of relativistic jets
Heating of external medium by jets