1. Particle acceleration in Supernova Remnants from X-ray observations Anne Decourchelle Service d’Astrophysique, CEA Saclay I- Ejecta dominated SNRs: Cas A, Tycho and Kepler II- Synchrotron-dominated SNRs: SN 1006, G347.3-0.5

2. Tycho (XMM-Newton) PWN in G0.9+0.1 (XMM-Newton) Shell SNRs and plerions =>Restriction to shell SNRs -> talk of Sidoli

3. Particle acceleration in SNRs Pending questions:  How efficient is cosmic-ray acceleration in SNRs ?  What is the maximum energy of accelerated particles ?  How large is the magnetic field ? Is it very turbulent ?  Is it amplified ?  No unambiguous evidence for ion acceleration in SNRs SNRs : main source of cosmic-rays with E ≤ 10 15 eV ? ► SNRs have enough total power ► Strong shocks in SNRs: First-order Fermi shock acceleration (radio emission → relativistic GeVelectrons) ► Composition of bulk of CRs, typical of mixed ISM → acceleration of ISM gas and dust by shocks in SNRs ► X-ray observations of synchrotron emission → TeV electrons

4. RADIUS Blondin and Ellison 2001, ApJ 560, 244 Decourchelle, Ellison, Ballet 2000, ApJ 543, L57 Efficient particle acceleration in young supernova remnants Interstellar medium 2 shocks =>Modification of the X-ray morphology and temperature of the gas

5. Cas A Radio Bleeker et al. 2001, A&A 365 XMM-Newton 8-15 keV Allen et al. 1997, ApJ 487, L97 Morphology of the X-ray continuum in young SNRs Strong radio emission “associated” with the ejecta => amplified magnetic field due to R-T instabilities at the interface ejecta/ambient medium Strong X-ray emission “associated” with the ejecta and weaker plateau in X-rays associated with the blast wave => inconsistent with synchrotron: non-thermal bremstrahlung ? Particle acceleration at secondary shocks ? (Vink & Laming 2003, pJ 584, 758) ? Cas A XMM-Newton 8-15 keV Bleeker et al. 2001, A&A 365 Radio

6. Thermal component: kT ~ 3.5 keV and n e t ~ 4 10 10 cm -3 s Non-thermal component: RIM: 84 % of the 4-6 keV continuum, power law  ~ 2.2 INSIDE: 11% of the 4-6 keV continuum, power law  > 4.5 =>width of the rim inconsistent with thermal emission Vink and Laming 2003, ApJ 584, 758 VLA radio X-ray continuum Chandra (x 10) Spectrum of the forward shock in Cas A

7. Cassam-Chenai et al., 2003, A&A in press DeLaney et al., 2002, ApJ 580, 914 Kepler (1604) XMM-Newton Si K Cassam-Chenai et al., 2003 Continuum associated with the forward shock: synchrotron emission ? Forward shock very close to the interface ejecta/ambient medium: R FS /R CD = 11/10: morphology expected when particle acceleration is nonlinear ! Shocked ejecta Shocked ambient medium Shocked ejecta => thermal non ionization equilibrium emission Shocked ambient medium => synchrotron emission using radio constraints: Maximum energy of accelerated electrons ~ 60 TeV XMM-Newton 4-6 keV Radio VLA XMM spectrum of the forward shock

8. Tycho (1572) Continuum associated with the forward shock: synchrotron emission ? Forward shock very close to the interface ejecta/ambient medium: R FS /R CD = 11/10: morphology expected when particle acceleration is nonlinear ! 4-6 keV Decourchelle et al. 2001, A&A 365, L218 No emission line features ! Thermal interpretation: kT = 2.1 keV and n e t = 10 8 cm -3 s => strong ionization delay but problem with the morphology Non-thermal interpretation: synchrotron X-ray power law:  ~ 2.8 Rolloff frequency: ~7 10 16 Hz => maximum electron energies ~ 1-12 TeV Broad band Radio 22cmcontinuum Chandra Chandra spectrum of the forward shock Hwang et al, 2002, ApJ

9. Time to move out  t =  r / u gas with u gas = 1/R*V sh, R: compression ratio Equating t loss and  t gives B. Cas A: D = 3.4 kpc, V sh ~ 5200 km/s, B  60-100  G Vink and Laming 2003, ApJ 584, 758 Tycho: D = 3.2 kpc, V sh ~ 4600 km/s, 4”,  t = 1.65  10 9 s => B  60  G Kepler: D = 4.8 kpc, V sh ~ 5400 km/s, 3”,  t = 1.59  10 9 s => B  60  G Sharp rims at the forward shock. Radiative ? Requires magnetic field amplification (Lucek and Bell 2000, MNRAS 314,65) or nonlinear particle acceleration and large compression ratio at the shock (~8) X-ray continuum Chandra Sharp filaments observed all along the periphery of these young SNRs => synchrotron emission, width determined by synchrotron losses of ultrarelativistic electrons

10. Morphology of the high energy X-ray continuum - Bright emission associated with the ejecta in Cas A: nonthermal bremsstrahlung. Particle acceleration at secondary shocks ? - Ejecta interface close to the forward shock in Kepler and Tycho => nonlinear particle acceleration with shock modification - Sharp filaments all along the rim => magnetic field randomly oriented around the 3 remnants (unlike in SN 1006) Forward shock: nature of the spectrum and width of the rim - Synchrotron emission at the forward shock => First order Fermi acceleration with electrons up to energies of 1-60 TeV - Sharp rims due to the limited lifetime of the ultrarelativistic electrons in the SNR =>large magnetic field values ~ 60-100  G derived for Cas A, Tycho, Kepler Amplification of the magnetic field or nonlinear particle acceleration with large compression ratio (>>4) ? Summary on particle acceleration in young SNRs

11. SN 1006: first evidence of electrons acceleration up to TeV energies (Koyama et al. 1995, Nature 378, 255) X-ray thermal emission in the faint areas X-ray synchrotron emission in the bright rims Power-law distribution of electrons, cut-off at high energy ν cut = 240 eV (Dyer et al. 2001, ApJ 551, 439)

12. (Tanimori et al. 1998, ApJ 497, L33) SN 1006, CANGAROO γ-ray emission Inverse Compton on 3 K CMB (or local photons) by the same TeV electrons emitting the X-rays by synchrotron  0 decay following nuclear reactions by the accelerated ions on the thermal gas Only spectral range where the protons may be directly detected (electrons make up only a few % of the energy density of CRs) or Synchrotron IC Radio νFννFν small B large B

13. SN 1006 with XMM-Newton : Geometry of the acceleration MOS images (square root scaling), 4 pointings GT Oxygen band (0.5 – 0.8 keV) : thermal emission 2 – 4.5 keV band : Non-thermal emission R. Rothenflug et al.

14. Transverse profile: principle How is the magnetic field oriented ? A symmetry axis seems to be running from south-east to north-west, BUT if the bright limbs were an equatorial belt, non-thermal emission should also be seen in the interior φ = π/3 In Out F in /F out > π/2φ – 1 = 0.5 If equatorial belt: F in /F out > 0.5 Observed: 0.8-2 keV: 0.300 ± 0.014 2-4.5 keV: 0.127 ± 0.074 => Polar caps

15. Radio/X-ray comparison Combined Molonglo + Parkes radio image at 843 MHz with 44" x 66" (FWHM) spatial resolution (Roger et al., ApJ 332, 940). Extract spectra in boxes just behind the shock all around the remnant, and as a function of radius toward the North-East XMM-Newton: 2 – 4.5 keV band RADIO

16. Spectral modelling North East South East Fit the spectra with a two-component model: synchrotron emission from a cut-off electron power law (SRCUT). thermal emission from a plasma out of ionisation equilibrium behind a shock (VPSHOCK) with variable abundances. Interstellar absorption fixed: N H = 7 10 20 cm -2. Slope of the e - power-law fixed: 2.2. (α = 0.6 in the radio) Normalisation of the synchrotron component fixed using the radio data => only the cut-off frequency was left free.

17. Cut-off frequency - Very strong azimuthal variations, cannot be explained by variations of the magnetic compression alone. => Maximum energy of accelerated particles higher at the bright limbs than elsewhere. - If B ~ 50 μG, the maximum energy reached by the electrons at the bright limb is around 100 TeV. ν cut (eV) ~ 0.02 B(μG) E 2 cut (TeV) Center Shock - Spatial variations of the cut-off frequency of the synchrotron emission exist in SN 1006. - The very strong radial variations confirm that the bright limbs look like polar caps. The X-ray geometry of SN 1006 favors cosmic-ray acceleration where the magnetic field was originally parallel to the shock speed (polar caps)

18. An extreme case of synchrotron-dominated SNR: G347.3-0.5 Uchiyama et al. 2002, PASJ 54, L73 ASCA GeV emission (EGRET) associated with cloud A ? Butt et al. 2001, ApJ, 562, L167 TeV emission (CANGAROO) in the NW: Inverse compton or  0 decay process ? Muraishi et al. 2000, A&A, 365, L57, Enomoto et al. 2002, Nature, 416, 25, Reimer & Pohl 2002, A&A, 390, L43 XMM-Newton results => talk of G. Cassam-Chenai