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Observational evidences of particle acceleration at SNRs

Observational evidences of particle acceleration at SNRs. Suzaku. Chandra. Aya Bamba (RIKEN, Japan) and Suzaku team. 0. Talk plan:. X-ray observation for cosmic-ray study topic 1: X-ray study on acceleration efficiency of electrons topic 2:

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Observational evidences of particle acceleration at SNRs

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  1. Observational evidences of particle acceleration at SNRs Suzaku Chandra Aya Bamba (RIKEN, Japan) and Suzaku team

  2. 0. Talk plan: • X-ray observation for cosmic-ray study • topic 1: • X-ray study on acceleration efficiency of electrons • topic 2: • X-ray study on acceleration possibility of protons • topic 3: • X-ray study on acceleration efficiency of protons • Summary

  3. 1.1. how to search accelerators? gyro radius of TeV e = a few pc sync. emission in hard X-rays X-rays are the best indicator TeV electron IS B (~mG) Koyama et al.(1995) Discovery of sync. X-rays from the shell of SN 1006 SN1006: type Ia d=2.18kpc 10´ Shocks of SNRs = cosmic ray accelerators! …. but details are unsolved

  4. 1.2. Remaining problems acc. efficiency of electrons acc. possibility of protons acc. efficiency of protons distribution of synch. X-rays (Chandra) -> topic 1 wide-band spectra (radio - TeV) (Suzaku) -> topic 2 plasma diagnostics in X-rays (Suzaku) -> topic 3 For all of these remaining problems, X-rays are the strong tool !

  5. 1.3. X-ray satellites Suzaku energy range Chandra spatial resolution effective area Each satellite has strong points XMM-Newton spectral resolution for diffuse sources

  6. Topic 1: X-ray diagnostics for acc. efficiency of electrons

  7. 2.1. observational information to solve • The spatial distribution • their gyro radius, the turbulence of B, …. • The spectrum of synchrotron emission • the maximum energy, B, …. • The age of the system • the evolution of acceleration Spatial resolution! Chandra has excellent spatial resolution (0”.5) best for such a study

  8. Happy Birthday! 2.2. In the case of SN 1006 Mei-Getsu-Ki (The diary of Teika Fujiwara) ancient samples of guest stars 3C58 Crab nebula Great guest star like Mars on 1006. May 1st

  9. 0.3 1 5 Energy (keV) 2.3. SN 1006 image upstream us = 2890km/s downstream thermal (0.24 keV) extended non-thermal sharp SN1006 NE shell 0.3 – 2.0 keV 2.0 – 10.0 keV Scale length of the filaments? (Bamba et al. 2003)

  10. 2.4. Fitting results wu 0.05 pc 0.01 pc wd 0.2 pc 0.05 pc Mean value………………. Minimum value………… 10´´ = 0.1 pc 2 – 10 keV First measurement of the width of filaments

  11. Non-thermal! Emax 100TeV 2 nrolloff = 5x1017Hz B 10mG Reynolds & Keohane (1999) 2.5. Spectral Fitting spectrum • Hard • No line SRCUT model 0.5 1 5 10 (keV) power-law exponential cutoff Sync. emission from electrons a = 0.57 @1GHz (fixed) (Allen et al. 2001) nrolloff = 2.6 (1.9 – 3.3) x 1017 Hz Flux = 1.8 x10-12 ergs cm-2s-1

  12. SRCUT model Spectrum of electrons Synchrotron emission from power-law electrons G N(E) exp. G-1 2 E Emax emission Synchrotron emission from a single e n nrolloff ~ Emax2B emission n EmaxB

  13. 2.6. Many young historical SNRs have thin filaments with sync. X-rays Cas A(SN1680) Kepler(SN1604) Tycho(SN1572) RCW 86 (SN184) SN1006 thin filaments are common in young SNRs (Bamba et al. 2005)

  14. 2.7. Why are filaments so thin? ….. Small diffusion in direction to shock normal! perpendicular B or parallel B ? perpendicular! Diffusion only occurs along the B ordered or turbulent B ? turbulent B turbulent → strongly scattered 　 → hardly go downstream → staying long around shocks high effic. (equipartition) First quantitative image ! shock up down Emax of electron 30-40 TeV The angle: > 85 deg. The strength: 10 – 80mG

  15. another scenario very strong parallel B (Berezhko et al. 2004) Strong B makes the gyro radius small → diffusion becomes small B ~ 100 – 400 mG shock up down Turbulent magnetic field (Bohm limit) Very efficient acceleration (equipartition) Anyway, First estimation of magnetic field structure

  16. 2.8. Time evolution of B observational facts func. of Bd wd ~ rgus-1 ~ EmaxBd-1us-1 nrolloff ~ Emax2Bd B = nrolloffwd-2 ~ Bd3us2 us ~ t-0.6 (Sedov) Direct estimations of the evolution ofB ONLY from the observational facts!

  17. (Bamba et al. 2005) +0.11 -0.06 nrolloff/wd2 ~ tage-2.96 (c2/d.o.f.=2.0/3) B = nrolloff/wd2 (Hz/pc2) 1017 1018 1019 1020 1021 1022 (Bd3us2) • 500 1000 2000 tage (years) Bd ~ tage-0.6 (Sedov)

  18. uA us uB = uCR B 4pr uA = (Lucek & Bell 2000) 2.9. Time evolution of energy densities thermal uth: ~ T ~ tage-1.2 Sedov kinetic ukin: ~ us2 ~ tage-1.2 Our result (Bd ~ tage-0.6) Magnetic energy density uB: ~ Bd2 ~ tage-1.2 CR energy density uCR: assumption: uCR ~ Bdus ~ tage-1.2 All energy densities have same time dependence! acc. efficiency for electron is very high!

  19. 2.10. Images Shock energy density thermal kinetic shock evolution In mag. field Non-linear Effect CR energy density mag. energy density interaction of mag. Field and CR strong interaction for each other In each filament: equipartition evolution keeping equipartition? We must consider these three energy density simultaneously!

  20. Topic 2: X-ray diagnostics for acc. possibility of protons

  21. 3.1. How to search proton accelerators ? The efficiency of electron acceleration is so high. however … How about protons ? electrons -> synch. X-rays + IC g-rays protons -> g-rays via p0 decay g-rays X-rays IC sync. E2 dF/DE p0 Energy To find out proton accelerators … searching for X-ray dim & g-ray bright sources TeV & X-ray observations are strong tool!

  22. 3.2. TeV gamma-ray observations HESS: TeV g-ray telescope @ Namibia Imaging Atmospheric Cherenkov Telescopes since 2004 http://www.mpi-hd.mpg.de/hfm/HESS/HESS.html They have done Galactic Plane survey for the first time.

  23. HESS J1834-087 HESS J1813-178 HESS J1825-137 HESS J1837-069 HESS J1804-216 Sgr A* They have no counterpart. New accelerator candidates? HESS J1640-465 HESS J1614-518 RX J1713 HESS J1616-508 Aharonian et al. 2005

  24. 3.3. A candidate of p accelerators ? … HESS unIDs along Galactic plane diffuse sources -> Galactic ? Their nature is unknown <- lack of counterparts With deep absorption on Galactic plane, follow-up obs. are very difficult. -> X-ray follow-up is needed !

  25. 3.4. Introduction of Suzaku The 5th Japanese X-ray satellite. It was launched on July 10th 2005. 朱雀(Suzaku) Suzaku is “Red Phoenix”, the protector God of the South. The wall painting of Suzaku in “Kitora” tomb

  26. 3.5. Instruments XRT (X-Ray Telescope) Large effective area 450cm2 @1.5keV XIS (X-ray Imaging Spectrometer) Improved X-ray CCD with high efficiency and good energy resolution Low Background Energy band : 0.2-12keV HXD (Hard X-ray Detector) Wide energy band Si-PIN (10-70keV) & Scintillator (30-600keV) Non-imaging detector, but low background XRT XIS Suzaku is best for follow-up of TeV unIDs ! HXD

  27. 3.7. One possible scenario for TeV unID sources: Emission from SNRs in various phases (Yamazaki et al. astro-ph/0601704) young SNRs large shock speed both e and p are accelerated strong synchrotron X-rays old SNRs small shock speed electrons are deccelerated no emission TeV unIDs are old SNRs colliding with MCs? Their nature is still unknown, but Suzaku will solve it ! SNRs colliding with MCs amount of targets strong p0 decay

  28. Topic 3: X-ray diagnostics for acc. efficiency of protons

  29. 2(g-1) (g+1)2 kTd = mvs2 kinetic E of shocks thermal E of downstream plasma thermal E of downstream plasma E of accelerated particles kinetic E of shocks kinetic Eof shocks 4.1. how to measure acc. efficiency of protons ? Thin thermal plasma (~keV) emits lines in the X-ray band. X-ray plasma diagnostics can determine precise plasma parameters. Suzaku XIS has good spectral resolution -> best for the study ! from Rankine-Hugoniot relation ~ 0.19 Eshock (no acc.) < 0.19 Eshock (efficient acc.)

  30. 5. Summary • We detected sync. X-rays from filaments in young SNRs. • The filaments are very thin ! • Thin filaments reveal us that the acc. efficiency of electrons is very high. • Suzaku deep observations reveal us that HESS unID sources might be proton accelerators. • They might be old SNRs ? • Suzaku will enable us to estimate the acc. efficiency of protons.

  31. Notice ! Suzaku is providing a lot of fruitful data, and many results of Suzaku observation are reported ! We will hold the conference “The Extreme Universe in the Suzaku Era” at Kyoto on December 4-8, 2006 ! Topics are not only SNRs but all high E topics. We are looking forward to your participating !! http://www-cr.scphys.kyoto-u.ac.jp/conference/suzaku2006/

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