Download presentation

Presentation is loading. Please wait.

Published byKimberly Connolly Modified over 2 years ago

1
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 YSO X-ray transients pulsars

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 time scales 10 yrs 7

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

7
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

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

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
Layer width velocity Layer width tracer Relativistic cases: correspondence at equal Mr = g v/ g s c s 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

12

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

14
Fanaroff-Riley classification FR II or lobe dominated classical doubles FR I or jet dominated Cygnus A VLA 3C 449 VLA

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 Brightness ratio between jet and counterjet in 3C31 3C272.1 VLBI one-sided jet VLA

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 jj e Jet Mach number Lorentz factor Density ratio

19
Mach 3, 30 Density ratio (lab frame) Lorentz factor 10 Low resolution 12 points over radius High resolution 25 points over radius Stretched grid in the transverse direction Increasing grid size Parameters values

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

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

22
1) The entrainment is mediated by the cocoon

23
M=30 =10 =10 t=265

24
1) 2)

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

26
Jet massExternal mass Jet mass External mass

27

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

29
CHANDRA HYDRA A X-RAY HYDRA A X - RADIO

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

33
NUMERICAL SIMULATIONS reflecting outflow reflecting 02.6 Initial density distribution Uniform temperature 1024x1024 grid points Jet inlet

34
UNITS

35
RESULTS

36

37
M Subsonic jet lc = 0.5 lc = 1 lc = 2 Strongly overpressured Weakly overpressured

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 0.5 keV 1 keV 2 keV

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

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

41
L-T relation L-T relation Entropy per particle (at ) 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

Similar presentations

© 2016 SlidePlayer.com Inc.

All rights reserved.

Ads by Google