Real vs. Simulated Relativistic Jets

1. José L. Gómez Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain Institut d’Estudis Espacials de Catalunya/CSIC, Barcelona, Spain Real vs. Simulated Relativistic Jets • Overview • Development of Relativistic Numerical Codes • What have we learned? • Observations of the inner jet • Interpretation using the simulations • What the future may bring Socorro 2003

2. 1995: 2D RHD+E Computation of the non-thermal emission from the HD results, allowing synthetic maps directly comparable with observations Gómez et al. (1995-7); Mioduszewski et al. (1997); Komissarov & Falle (1997); Agudo et al. (2001) Gómez et al. (1997) 1996: 2D RMHD First studies of the magnetic field influence in the flow of relativistic jets van Putten (1996); Koide et al. (1996); Komissarov (1999) Relativistic Numerical Codes 1993-4: 2D RHD First Relativistic HD codes capable of solving the conservation equations for rest-mass and energy-momentum van Putten (1993); Martí et al. (1994-5-7); Duncan & Hughes (1994); Falle & Komissarov (1996) Martí et al.

3. Aloy et al. (1999) 1998: GRMHD First Simulations for General Relativistic MHD mainly aimed to study jet formation Koide et al. (1998,1999,2002); Meier et al. (2001); Gammie et al. (2003); de Villiers & Hawley (2003) Koide et al. (1999) 1999: 3D hr-RHD 3D high resolution RHD simulations Aloy et al. (1999, 2000); Hardee (2000); Hughes et al. (2002) 2003: 3D hr-RHD+E First computation of synthetic images, including all relativistic effects (time delays), from high resolution 3D RHD simulations by Aloy et al. (2003) Relativistic Numerical Codes 1997: 3D RMHD Extension to 3D RMHD by Nishikawa et al. (1997-8)

4. Structural position angle vs. time • Evidence for jet in precession • Inner (outer) ballistic (non-ballistic) motions BL Lac by Stirling et al. (2003) What have we learned? Inner Jet Structure The VLBA has allowed to monitor multiple sources with unprecedented time and spatial resolutions. Some of the programs (not a complete list): • 3-year of bi-monthly polarimetric 43 GHz observations of 15 sources including 3C279, 3C273, BL Lac, OJ287, etc. Big collaboration by Marscher, Jorstad, et al. • Further information (images & movies) in: http://www.bu.edu/blazars/research.html See also poster by Jorstad et al. Further BL Lac studies by: Denn et al. (2000) Gabuzda & Cawthorne (2003)

5. 3C279 at 22 GHz Wehrle et al. (2001) What have we learned? Inner Jet Structure The VLBA has allowed to monitor multiple sources with unprecedented time and spatial resolutions. Some of the programs (not a complete list): • 22 and 43 GHz VLBA observations of 3C279 A kinematical analysis shows indications of inward motions for a component associated with a jet recollimation shock.

6. Close to the core associated with recollimation shocks • Farther down the jet associated with bends What have we learned? Inner Jet Structure The VLBA has allowed to monitor multiple sources with unprecedented time and spatial resolutions. Some of the programs (not a complete list): • Motions in a sample of 42 -ray bright blazars Jorstad et al. (2001) Most of the sources present stationary features:

7. What have we learned? Inner Jet Structure The VLBA has allowed to monitor multiple sources with unprecedented time and spatial resolutions. Some of the programs (not a complete list): • 22 and 43 GHz polarimetric long-term (20+12 epochs) monitoring of 3C120 by Gómez et al. Gómez et al. (2000, 2001)

8. What have we learned? Inner Jet Structure The VLBA has allowed to monitor multiple sources with unprecedented time and spatial resolutions. Some of the programs (not a complete list): • 22 and 43 GHz polarimetric long-term (20+12 epochs) monitoring of 3C120 by Gómez et al. • The “head” of the component (o1&02) moves at a constant velocity of 4.4 c • Subluminal trailing components appear in the wake of the main feature Gómez et al. (2000, 2001)

9. What have we learned? (Real vs. Sim.) • Observations show: • Jet precession is increasingly common • Mixture of ballistic motions and components moving in curved paths • Coexistence of stationary and moving features, presenting complex variability • Indications of inwards motions and trailing components • Very complex polarization structures, suggestive of shocks, but also of toroidal and oblique fields • Jet/external medium and clouds interactions Simulations say:

10. Mioduszewski et al. (1997)  Emissivity Doppler Boosting at 30o Emission is determined by a complex combination of emissivity and Doppler boosting 60o 90o Darker gray means higher value What have we learned? 2D Sim. of Jet Perturbations First 2D+ RHD+E simulations Aimed to study the relationship between superluminal components and shocks (Marscher & Gear 1985) • Mioduszewski et al. (1997): Lorentz factor modulation between 1 and 10 at the jet inlet leading to a series of knots. • Komissarov & Falle (1997): Generation of standing and moving features. Time-delay effects allow to study superluminal motions.

11. Synthetic maps including all relativistic effects (time-delays) Stationary model Time • Recollimation shocksStationary comps. • Perturbation Superl. comp. • Interaction between both leads to: • Temporal dragging of the “stationary” • Inward phase motion of the “stationary”, as claimed by Wehrle et al. (2001) for 3C279 • A good temporal sampling is needed for a correct components’ identification • Measured apparent velocities may depend on observing frequency (resolution) What have we learned? 2D Sim. of Jet Perturbations First 2D+ RHD+E simulations Aimed to study the relationship between superluminal components and shocks (Marscher & Gear 1985) • Gómez et al. (1997): Simulation of an over-pressured jet, with =4, in which a short increase in  from 4 to 10 is included. Gómez et al. (1997)

12. What have we learned? 2D Sim. of Jet Perturbations Simulation: Light =4 jet in pressure equilibrium with the external medium Shock:Generated by introducing a short living perturbation in the injection Lorentz factor (=4 to 10) and an increase in pressure by a factor of 2 Agudo et al. (2001) Interaction of the shocked material with the external medium and the underlying jet leads to the formation of “trainling Shocks”. Computation of the emission by solving the transfer equations for synchrotron radiation at the retarded times

13. Space-Time diagram for the components in 3C120 What have we learned? 2D Sim. of Jet Perturbations Main shock produces a superluminal component Main Component Multiple trailing components appear in the wake of the main feature Trailings Agudo et al. (2001) • The inner structure in the jet of 3C120 can be interpreted as produced by “trailing components” (Gómez et al. 2001). Further evidence for trailing components in Centaurus A (Tingay et al. 2001) and other sources (Jorstad et al. 2001) • A single perturbation can produce multiple components • The emission structure variability can be interpreted with a smaller activity of the central engine (black hole + disk)

14. =5 Jet p p & v Wave-wave interactionsStationary comps. Individual wave patterns Moving. comps. Complex changing structure of coexisting stationary and moving components  Hughes et al. (2002) Hardee et al. (2001) Line-of-sight integration of p2 for a =2.5 precessing jet What have we learned? 3D Simulations 3D RHD: Jet response to precession First 3D RHD simulations are dedicated to study the propagation and stability of jets in precession. Aloy et al. (1999,2000); Hardee et al. (2001); Hughes et al. (2002) • Hardee et al. (2001) Interaction of the helical surface and body wave modes leads to enhancement in the line-of-sight images. The modes are triggered with a fixed phase difference at the inlet, and present different mode wavelengths:

15. What have we learned? 3D Simulations HST Image (Perlman et al. 2001) C HST D E G I A B Simulated intensity image Lobanov, Hardee & Eilek (2003) M87 intensity distribution is interpreted as resulting from the interaction of helical and elliptical modes. See also poster by Lobanov, Hardee & Eilek

16. What have we learned? 3D Sim. of Jet Perturbations Simulation: 3D hr-RHD+E of a precessing with with traveling perturbation Light (=10-3), relativistic (=6), precession pitch angle of ~2o Shock:Perturbation with a 4 times increase in density and energy during 0.8Rb/c Aloy et al. (2003) • Blue for the jet surface • White for the Lorentz factor • Color gradient for pressure • Precession leads to jet/external medium interactions • Component initially moves ballisticaly, leading to interactions with the external medium that increase its internal pressure

17. Observer’s reference frame Time delays stretches the structure as seen in the observer’s frame 10 Rb Pink shows  3 Rb Green shows  What have we learned? 3D Sim. of Jet Perturbations  Time  The perturbation evolves splitting into two (A,B) different regions

18. What have we learned? 3D Sim. of Jet Perturbations • Standing components associated with the recollimation shocks • New stretched region with increased emission • Associated peak brightnessmotion reflects changes in the internal distribution • Upstream motionsduring moving/standing components interaction

19.  What have we learned? 3D Sim. of Jet Perturbations • Standing components associated with the recollimation shocks • New stretched region with increased emission • Associated peak brightnessmotion reflects changes in the internal distribution • We only “see” the back portion of the perturbation Viewing angle selection effect

20. Space-Time diagram What have we learned? 3D Sim. of Jet Perturbations • Standing components associated with the recollimation shocks • New stretched region with increased emission • Associated peak brightnessmotion reflects changes in the internal distribution • We only “see” the back portion of the perturbation. Viewing angle selection effect • Slow moving “helical” components Helical component

21. What have we learned? 3D Sim. of Jet Perturbations • Standing components associated with the recollimation shocks • New stretched region with increased emission • Associated peak brightnessmotion reflects changes in the internal distribution • We only “see” the back portion of the perturbation. Viewing angle selection effect • Slow moving “helical” components • Its ballistic motion leads to a differential brightness distribution across the jet width Aloy et al. (2003)

22. What have we learned? (Real vs. Sim.) • Observations show: • Jet precession is increasingly common • Mixture of ballistic motions and components moving in curved paths • Coexistence of stationary and moving features, presenting complex variability • Indications of inwards motions and trailing components • Very complex polarization structures, suggestive of shocks, but also of toroidal and oblique fields • Jet/external medium and clouds interactions • Simulations say: • Over-pressured jets may lead to recollimation shocks, i.e., standing features • Superluminal components may be obtained from different perturbations at the jet inlet (, p, ) • Complex interactions between moving and standing shocks leading to inward motions and frequency dependent apparent velocities • Equally complex for wave-wave interactions • Trailing shocks may be expected • Time delays stretches internal shocked structure, which appearance depends on the viewing angle (selection effect) • General good agreement between Observations and Simulations, proving one of the most powerful tool for the study of relativistic jets • Expect very complex internal jet structure variability. Shock-in-jet models (1-component-1-shock) may be an over-simplistic idealization • Perhaps it is time to forget about Gaussian model fits and start paying attention to the image pixel. Good time samplings are required

23. What the future may bring • Open questions: • Mechanisms of jet formation, collimation, and acceleration • What is the role played by the magnetic field? • What is the jet composition? • Better understanding of the superluminal and stationary features • Jet/external medium and clouds interactions. Is it important at pc-scales? • Emission at “high” energies (optical, x-rays, -rays) • Particle acceleration and electron aging along the jet and radio lobes • Numerical simulations: • RMHD models allow to study: • Acceleration and collimation • Polarization in components • Jet Stratification • GRMHD models: • Jet formation • New EOS • Jet composition RHD + Emission Models • Electron energy transport • Radiative losses (e- aging) and particle acceleration • Inverse Compton (SSC, EC) • High energy emission 3D GRMHD + Emission models + Microphysics (EOS, e-, part. acc., ...)