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Supernov æ as Cosmic-ray sources

Supernov æ as Cosmic-ray sources. Isolated Supernov æ. A. Marcowith (L.P.T.A.). Outlines. The Galactic cosmic-ray (GCR) spectrum & the supernova hypothesis. The standard model of Galactic cosmic ray Multi-wavelength observations Diffusive shock acceleration

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Supernov æ as Cosmic-ray sources

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  1. Supernovæ as Cosmic-ray sources Isolated Supernovæ A. Marcowith (L.P.T.A.)

  2. Outlines • The Galactic cosmic-ray (GCR) spectrum & the supernova hypothesis. • The standard model of Galactic cosmic ray • Multi-wavelength observations • Diffusive shock acceleration • Turbulence in supernova (SN) shocks • Conclusions

  3. The galactic cosmic rays • The Cosmic-ray spectrum • The supernova hypothesis Standard books: Berezinsky ’90, Gaisser ’94, Schlickeiser ’03.

  4. Galactic Cosmic rays eV The Cosmic-ray spectrum

  5. The Supernova hypothesis Hypothesis: Same CR energy density in the galactic disc. • Local energy density of GCRs: E ~ 1 eV/cm3(@ 1 GeV) • Power necessary to supply CRs: Pcr = V E / tr ~ 1041 erg/s • Typical power (of type II) SN (majority of SN in Spiral galaxies): PSN ~ 3 x 1042 erg/s Pcr ~ few % PSN Supernovae are the main sources of GCR

  6. Type I Type II WITHOUT H Absorption lines WITH H Absorption lines Massive star collapse Type Ib & Ic Type Ia Ib He lines Ic no He & no Si lines No He lines Si lines White dwarf/giant system explosion Type of Supernova • SN frequency (Nb/century/Galaxy) SNII ~ 0.88 SNIa ~ 0.24 SNIbc ~ 0.16

  7. Tycho SN remnant Crab remnant & nebula Type Ia Type II Both processes inject ~ 1051ergs into ~ 1 solar mass…

  8. Historical galactic Supernovæ www.seds.org/Messier/more/mw_sn.html Clark & Stephenson ‘77

  9. Outlines • The Galactic cosmic-ray (GCR) spectrum & the Supernova hypothesis • The standard model of Galactic cosmic ray • Multi-wavelength observations • Shock acceleration • Conclusions

  10. The standard model of GCRs • SN evolution phases • Effects of the environment • Diffusive shock acceleration - Test particle solutions. • GCRs propagation [see R.Terrier & M. Lemoine] • GCRs composition

  11. Supernova evolution phases • 3 main phases: • Free expansion • Self-similar expansion or Sedov-Taylor • Radiative phase • Fiducial case: SN explosion with uniform ejecta and E0= 1051 erg, Mej= 1 solar mass, standard ISM with uniform ext = 10-24 g/cm-3

  12. Free expansion phase [100-103 yrs] • SN explosion  supersonic expansion  shock. • The free expansion stage starts once the shock reaches the edge of the atmosphere of the star. • Mechanical energy  kinetic energy. MSNR = Mej: ejecta dominated phase VSNR ~ (2 E0/ Mej)1/2= cst RSNR = VSNR t • Fiducial SN: VSNR ~ 5000 km/s

  13. ejecta Ambient ISM Reverse shock • The shocked ISM is heated and compressed by the blast wave  pushes on the ejecta back  the ejecta are compressed and heated  Reverse shock.

  14. Self-similar phase [103-104 yrs] • MSNR = Mswept-up = 4/3 ISM RSNR3: swept-up material dominated phase • The remnant interior has been heated by the reverse shock and the remnant expands bounded by the blast wave. • Evolution laws: RSNR  t 2/5 VSNR  t -3/5

  15. Self similar expansion laws • Energy in the remnant (1) • RH: Pressure eq. interior/shell (2) • RH: Velocity expansion (3) • (2) & (3)  (1) and MSNR  RSNR3  RSNR =  (E0 t2/0)1/5 • Sedov (1959) solved the stationary spherical HD Eq   ~ 1.1516 for  = 5/3

  16. Adiabatic phase: numerical 1D results • Truelove & McKee ‘99 Rt2/5 Rt

  17. Radiative phase [104-105 yrs] • 2 sub-phases: cool  exp (see Cioffi et al ’88) • Pressure conserved phase • Momentum conserved phase Pressure conserved phase (snowplough phase) • The swept-up collapse into a dense and thin shell • The interior expands adiabatically and pushes the shell like a snowplough • Energy not conserved (radiated away), Pressure conserved. Momentum conserved phase • Pressure Equilibrium: PSNR=PISM • No force is acting on the remnant, its momentum is conserved.

  18. Expansion laws: Summary

  19. Sedov-Snowplough transitions • Free expansion  Sedov: • Sedov  Snowplough: tST  273 yr, RST  3.7 pc, tSP  4.4x104 yr, RSP  25 pc

  20. Radius Shock Velocity Environment/Ejecta effects • Environment is not uniform[see Lecture II] - Molecular clouds, cavities in the ISM, galactic density gradients - Wind (  r-2), radiation of a massive star in type II SN (see SN1987A). • Strong influence of the circumstellar shell [Dwarkadas ’05, Chevalier ‘82] • = Shell mass/ Ejecta mass = 3.5

  21. Ejecta are not uniform: - Ejecta profiles  structure of the pre-SN star. - Parametric representation:  w-n t-3, w=v/vej, vej= initial velocity of the gas at the outermost surface of the ejecta - SNII: steep n ( 10) - SNIa: exponential profiles. • Detailed discussions in Dwarkadas ’05, Truelove & McKee ’99, Matzner & McKee ’99 • Influence on the blast wave dynamics in the stellar envelope  on the shock velocity.

  22. Diffusive shock acceleration & source spectra • Diffusive shock acceleration • Test-particle solutions • SN phases & CR acceleration See J. Kirk lectures

  23. // shock Udown=Uup/r Uup=Ush Downstream escapes at const. probability  Dup Ddown Efficient pitch-angle diffusion V ~ c >> ush, f is nearly isotropic Diffusive shock acceleration: in short

  24. Test-particle solutions • Microscopic treatement: - Constant energy gain at each cycle + constantprobability to escape downstream  scale invariant spectrum Stationary solutions: N(p)  p-1-Pesc/[p/p]  s = 3r/(r-1) = 4 for r = 4. • Acceleration timescale:

  25. SN phases and CR maximal energy • Free-expansion phase: Rapid expansion + steep ejecta profiles  adiabatic losses • The acceleration timescale  vsh-2  vsh  Snowplough phase • Sedov phase: SN dynamics controlled by the swept-up ISM. CR are injected from ISM gas. - Maximum CR energy fixed by the SN age: Emax  (Vsh2 t)  t-1/5 The highest CRs are accelerated in the transition Free expansion-Sedov [Lagage & Cesarsky ’83, Kirk’94]

  26. CR spectrum • Onion-shell model: Acceleration at the shock + adiabatic losses downstream [Bogdan & Voelk ’83] Ftot(p)= iFi(p,rsh(ti), si) (Fi particle distribution produced at radius r=rsh(ti) in Sedov expansion, sol. of a diffusion-convection Eq.)  Ftot(p)  p-4.1

  27. CRs composition (at earth) • At zeroth order: GCR and solar abundances are similar. • LiBeB/CNO are 106 more abundant in GCR • (also for subFe elements) • GCR = accelerated solar coronal material + propagation in the ISM (spallation, energy losses) ? 70-280 MeV/A 1-2 GeV/A (p+Fe) Sc-Ti-V-Cr-Mn (p+C/O) Li-Be-B

  28. CRs propagation • See lectures by R. Terrier, M. Lemoine

  29. GCR source composition SS: Anders & Grevesse GCR: CRIS/ACE • Source spectrum has similar abundances / solar system • GCR are accelerated from ordinary ISM • Not as clear; see Lecture II ….

  30. Standard CR model • SNR hypothesis • Energetics • Spectrum (DSA, SNr dynamics) • Maximum energy(see next) • Composition(see lectures II)

  31. Outlines • The Galactic cosmic-ray (GCR) spectrum & the Supernova hypothesis • The standard model of Galactic cosmic ray • Spectral energy distribution • Shock acceleration • Conclusions

  32. Spectral energy distribution • Radio • Infra-red • Optical lines • X-rays • Gamma-rays

  33. Radio (theory): synchrotron emission • Emission by relativistic (GeV) electrons accelerated at shocks (f / r) or/and by MHD turbulence. • Frequency MHz = [16.5] x BG x EGeV2 sin() • Non-thermal spectraF  -related to particle distribution Ne E-q by  = (q-1)/2. • Polarisation = (q+1)/(q+7/3)~70% for q = 2 • MF derived by Faraday rotation [see Lect.II] RM =  ne B// ds [cm-3 G pc]

  34. Radio (observation) I • Morphology: Limb-brightened radiation, spectral softening behind the blast wave [Delaney et al’02, Kepler]

  35. Radio (observation) II • Indices:  [0.4-0.7] (0.05)  q [1.8,2.4]  peak at  ~ 0.55  Good agreement with DSA linear theory. •  < 0.5 requires more observations/alternative explanations • Polarisation: a few % (<<70%)  high degree of disorder + effects of integration along the l.o.s.  SNr catalogue: 265 objects http://www.mrao.cam.ac.uk/surveys/snrs/[Green ’04]

  36. Radio observation: magnetic field structure • Radial structure  Rayleigh-Taylor instability [Milne ‘88]in young SNr • Transverse structure in older remnants  Compression at forward shock Képler Delaney et al ‘02

  37.  - D relation •  = mean surface • brightness = Radio luminosity per unit surface • D diameter.   D-2.4 Sample of 37 galactic SNr Case & Bhattacharya ‘98

  38. Infra-red • IR produced by dust heating (Spitzer observations , Hines et al’04) • Weak IR synchrotron: Cassiopae A[Rho et al’03, Jones et al’03, Tuffs et at.’97] - PolarisationP(%, 2.2m) = 4-10%  P(%, 6cm) - Radial magnetic field profiles. - IR (2.2 m) and radio (6 cm) images correlate each other. - (20-6 cm) = 0.76 and (6 cm-2.2 m) = 0.7  IR flux higher than expected

  39. Optical lines • Non-radiative lines (H Balmer lines): H, H collisional excitation of neutrals with post shock ions  Directly slow neutrals/fast ions: Narrow lines Indirectly fast neutrals produced form charge exchange from fast ions: Broad lines. - Broad Line width  Proton post shock thermal To - Broad/narrow line flux ratio  feq (fraction of thermal post shock energy for e-), Shock velocity.

  40. Compare observations with radiative transfer calculations [Ghavamian et al’01]  Tycho (knot g) feq < 0.2 (Te/Tp < 0.1)  vsh = 1.9-2.3 103 km/s.

  41. Kepler SNR in X-rays Si S Ar Ca ISM Fe X-rays • Thermal X-rays of shock heated gas at a few 106 K. - Heavy metals lines (O to Fe) produced by metal rich ejecta. • Non-thermal X-rays: - Under 10 keV: cut-off domain of synchrotron radiation of shock accelerated electrons (see next) - Above 10 keV: Unclear origin either synchrotron or Bremsstrahlung (Vink & Laming ’03) Court. J.Ballet

  42. X-ray imaging Cas A

  43. X-ray filaments • Few arc second sizes (Chandra 4-6 keV continuum) • Observation in young SNr [Ballet ’06, AM’06] • Tycho, CasA, Kepler, SN1006, G347.3-0.5, RCW86,G28.6-0.1 • Synchrotron radiation of TeV electrons [Ballet ’06] Bamba et al’06

  44. Multi-wavelength profiles Cas A • High angular resolution observations (Chandra, VLA) : blast wave radiation [Gotthelf et al ’01] • Cas A: NT X-ray emission peaks at the interface Blast wave

  45. SN1006 Thin black: 0.5-0.8 keV; Thick black: 1.2-2.0 keV; gray: radio Long et al’03

  46. Gamma-rays • EGRET • Tcherenkov & HESS observations

  47. GeV SNRs • Sturner et al ’96: 2nd EGRET catalogue  7 objects (among which IC443, Cygni, Monoceros, W44, W28). Interacting with molecular clouds ? • Torres et al ’03: 3rd EGRET catalogue  26 objects. Diamonds: EGRET Unidentified sources Circles: SNR from the Green catalogue

  48. TeV (confirmed) SNR SN1006 • Before HESS:  Cangaroo (SN1006, RXJ1713.7-3946, Tanimori et al’98, Muraishi et al’02)  HEGRA (CasA, Aharonian et al’02, TBC) • HESS did not confirm SN1006 [Aharonian et al ’05a]  Detection of RXJ1713.7-3946, Vela Junior. • 2 SNR in the galactic survey [Aharonian et al’04, 05b]  Total: 4-5 sources RXJ0852

  49. RXJ1713.7-3946 • First spectro-imagery at TeV of a SNR. • Non-significative indices variation across the remnant. • Possible correlation with molecular cloud.

  50. Dense targets • Gamma-ray emission process: • Inverse Compton (e-) e- + CMB/IR e- +  E ~ 4/3 (E/mec2)2 ECMB/IR (Thomson regime) • Non-thermal Bremsstrahlung (e-) e- + p+  e- + p+ +  E ~ Ep/2 • Neutral pion decay (p+) p+ + p+  p+ + p+ + 0 ; 0  2 E ~ Ep/6 Case of an electron/CR distribution: ne/CR E-se/sp

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