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INAF - Osservatorio Astronomico di Torino

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1 INAF - Osservatorio Astronomico di Torino
SIMULATIONS OF ASTROPHYSICAL JETS Gianluigi Bodo, Claudio Zanni, Attilio Ferrari, Silvano Massaglia, A. Mignone, P. Rossi INAF - Osservatorio Astronomico di Torino Università di Torino

2 Collimated, supersonic outflows (jets)
are generated in many astrophysical environments AGN pulsars YSO X-ray transients

3 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)

4 YSO jets HST images HH 30 1" 10''

5 AGN Jets Scales up to Mpc Non-thermal synchrotron radiation
Collimation angle can be few degrees Observed at different energies 7 time scales 10 yrs

6 BASIC PROBLEMS Launching Launching phase: acceleration from disk and collimation • Propagation Propagation phase: confinement, stability, entrainment • Termination Termination: interaction with external medium

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

8 Algorithms Time Stepping HD RHD MHD RMHD Riemann Solvers Interpolation
Fwd Euler (Split/Unsplit) RK 2nd (Split/Unsplit) RK 3rd (Split/Unsplit) Hancock (Split/CTU) Characteristic Tracing (Split/CTU)       (split)    (split)  Riemann Solvers Riemann (non-linear) TVD/ROE HLL HLLC TVDLF             Interpolation Prim. TVD-limited (II order) Characteristic TVD-limited Piecewise-Parabolic Multi-D Linear Interpolation 2nd and 3rd order WENO                

9 Stability of jets Kelvin-Helmholtz instability Transfer of momentum, entrainment Effects on the jet evolution Consider first a simple case, simple planar shear layer Velocity profile Vx = tanh y AGN: relativistic case

10 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

11 Relativistic cases: correspondence at equal Mr = gv/gs 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 Layer width tracer Layer width velocity


13 JET STABILITY Bodo et al. 1998 Linear phase Acoustic phase Mixing

14 Fanaroff-Riley classification
VLA FR I or jet dominated Cygnus A VLA FR II or lobe dominated “classical doubles”

15 Jet velocities No direct velocity measures
Evidences for relativistic motions on pc scale come from: Superluminal motions Jet one-sidedness Rapid variabilities High brightness temperatures

16 In FRI radiosources jets on kpc scale become symmetric
VLBI one-sided jet VLA Brightness ratio between jet and counterjet in 3C31

17 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 perturbed at the inlet

18 Physical parameters Jet Mach number Lorentz factor G Density ratio h
M G r j r e Jet Mach number Lorentz factor G Density ratio h

19 Parameters values Mach , 30 Density ratio (lab frame) Lorentz factor Low resolution 12 points over radius High resolution 25 points over radius Stretched grid in the transverse direction Increasing grid size

20 3D Numerical Simulation
Grid: 300x800x300 Jet injection+ perturbation outflow

21 1) M=3 h=1000 G=10 t=760

22 1) The entrainment is mediated by the cocoon

23 M=30 h=10 G=10 t=265

24 1) 2)

25 1) M=3 h=1000 G=10 t=760 2) M=30 h=10 G=10 t=265 Faster deceleration
Strong pinching due to high pressure cocoon Short wavelength mode  more efficient for entrainment 2) M=30 h=10 G=10 t=265 Helical mode

26 Jet mass External mass Jet mass External mass


28 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


30 CHANDRA Perseus A X - radio Perseus A X-ray

31 OBSERVATIONS X-ray cavities corresponding to radio lobes
Shells surrounding the cavities Shell temperature equal or lower than the surrounding medium Weak shocks

32 L-T relation for cluster gas

outflow Initial density distribution 2.6 Uniform temperature reflecting outflow 1024x1024 grid points Jet inlet reflecting 2.6




37 Subsonic jet Strongly overpressured Weakly overpressured M n lc = 2

38 Similar setup as before Larger grid, Longer integration times, longer than the lifetime of the radiosource Three cases with cluster of different scales: T keV 1 keV 2 keV

39 Entropy and dissipated energy
Borgani et al. (2002) Efficiency

40 Hydrostatic equilibrium
Lloyd-Davies et al. (2000)

41 L-T relation Entropy per particle First stage, future: insert heating
at z > 0 on protoclusters and follow the evolution with a cosmological simulation

42 Summary Single shear KH instability Deceleration of relativistic jets Heating of external medium by jets

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