1 / 18

Particle acceleration in Supernova Remnants from X-ray observations

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. Shell SNRs and plerions. =>Restriction to shell SNRs.

armina
Download Presentation

Particle acceleration in Supernova Remnants from X-ray observations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  3. Particle acceleration in SNRs SNRs : main source of cosmic-rays with E ≤ 1015 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 → TeVelectrons 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

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

  5. 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) ? Allen et al. 1997, ApJ 487, L97 Cas A Cas A XMM-Newton 8-15 keV XMM-Newton 8-15 keV Radio Radio Bleeker et al. 2001, A&A 365 Bleeker et al. 2001, A&A 365

  6. Spectrum of the forward shock in Cas A Vink and Laming 2003, ApJ 584, 758 X-ray continuum Chandra VLA radio (x 10) Thermal component: kT ~ 3.5 keV and net ~ 4 1010 cm-3s Non-thermal component: RIM: 84 % of the 4-6 keV continuum, power law a ~ 2.2 INSIDE: 11% of the 4-6 keV continuum, power law a > 4.5 =>width of the rim inconsistent with thermal emission

  7. XMM-NewtonSi K XMM-Newton4-6 keV Radio VLA Shocked ambient medium Shocked ejecta DeLaney et al., 2002, ApJ 580, 914 Kepler (1604) Cassam-Chenai et al., 2003, A&A in press Cassam-Chenai et al., 2003 • Continuum associated with the forward shock: • synchrotron emission ? • Forward shock very close to the interface ejecta/ambient medium: RFS/RCD = 11/10: • morphology expected when particle acceleration is nonlinear ! XMM spectrum of the forward shock Shocked ejecta => thermal non ionization equilibrium emission Shocked ambient medium => synchrotron emission using radio constraints: Maximum energy of accelerated electrons ~ 60 TeV

  8. Chandra spectrum of the forward shock continuum Radio 22cm Broad band Chandra Chandra Hwang et al, 2002, ApJ 4-6 keV Decourchelle et al. 2001, A&A 365, L218 No emission line features ! Thermal interpretation: kT = 2.1 keV and net = 108 cm-3s => strong ionization delay but problem with the morphology Non-thermal interpretation: synchrotron X-ray power law: a ~ 2.8 Rolloff frequency: n ~7 1016 Hz => maximum electron energies ~ 1-12 TeV • Tycho (1572) • Continuum associated with the forward shock: • synchrotron emission ? • Forward shock very close to the interface ejecta/ambient medium: RFS/RCD = 11/10: • morphology expected when particle acceleration is nonlinear !

  9. Sharp rims at the forward shock. Radiative ? 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 Time to move out t = r / ugas with ugas = 1/R*Vsh , R: compression ratio Equating tloss and t gives B. Cas A:D = 3.4 kpc, Vsh~ 5200 km/s, <4", t < 1.56109 s=> B  60-100 G Vink and Laming 2003, ApJ 584, 758 Tycho:D = 3.2 kpc, Vsh~ 4600 km/s, 4”, t = 1.65109 s=> B  60 G Kepler:D = 4.8 kpc, Vsh~ 5400 km/s, 3”, t = 1.59109 s=> B  60 G Requires magnetic field amplification (Lucek and Bell 2000, MNRAS 314,65) or nonlinear particle acceleration and large compression ratio at the shock (~8)

  10. Summary on particle acceleration in young SNRs • 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) ?

  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 • νcut = 240 eV (Dyer et al. 2001, ApJ 551, 439)

  12. γ-ray emission Synchrotron νFν IC Radio SN 1006, CANGAROO (Tanimori et al. 1998, ApJ 497, L33) or large B small B • 0 decayfollowing 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) • Inverse Compton on 3 K CMB (or local photons) by the same TeV electrons emitting the X-rays by synchrotron

  13. SN 1006 with XMM-Newton : Geometry of the acceleration R. Rothenflug et al. 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

  14. φ = π/3 Out In 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 => Polar caps If equatorial belt:Fin/Fout > 0.5 Observed: 0.8-2 keV: 0.300 ± 0.014 2-4.5 keV: 0.127 ± 0.074 Fin/Fout > π/2φ– 1 = 0.5

  15. Radio/X-ray comparison XMM-Newton: 2 – 4.5 keV band RADIO 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

  16. NorthEast Spectral modelling • 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: NH = 7 1020 cm-2. • Slope of the e- power-law fixed: 2.2. • (α = 0.6 in the radio) • Normalisationof the synchrotron component fixedusing theradio data • => only the cut-off frequency was left free. SouthEast

  17. Cut-off frequency Center - Spatial variations of the cut-off frequency of the synchrotron emission exist in SN 1006. - The very strong radial variationsconfirm that the bright limbs look like polar caps. Shock - Very strong azimuthal variations,cannot be explained byvariations of themagneticcompressionalone. => Maximum energyof accelerated particles higher at the bright limbsthan elsewhere. - If B ~ 50 μG, the maximum energy reached by the electrons at the bright limb is around 100 TeV. νcut(eV) ~ 0.02 B(μG) E2cut (TeV) 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 ASCA XMM-Newton results => talk of G. Cassam-Chenai Uchiyama et al. 2002, PASJ 54, L73 TeV emission (CANGAROO) in the NW: Inverse compton or p0 decay process ? Muraishi et al. 2000, A&A, 365, L57, Enomoto et al. 2002, Nature, 416, 25, Reimer & Pohl 2002, A&A, 390, L43 GeV emission (EGRET) associated with cloud A ? Butt et al. 2001, ApJ, 562, L167

More Related