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Supernov æ as Cosmic-ray sources

Supernov æ as Cosmic-ray sources. II. Massive star formation regions & Superbubbles. A. Marcowith (L.P.T.A.). Outlines. OB association (OBa) and Super-bubbles (SB): a short overview. Massive stars clusters Supernov æ in Super-bubbles

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Supernov æ as Cosmic-ray sources

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  1. Supernovæ as Cosmic-ray sources II. Massive star formation regions & Superbubbles A. Marcowith (L.P.T.A.)

  2. Outlines • OB association (OBa) and Super-bubbles (SB): a short overview. • Massive stars clusters • Supernovæ in Super-bubbles • Multi-wavelength observation of galactic and extragalactic OBa/SB • Turbulent SB • SB as cosmic-ray sources • SB as high energy sources • Conclusions

  3. OB association and Super-bubbles Doradus 30 in LMC (Chandra)

  4. Supershell GMC T > 106 K 300 pc OBassociation n ~ 10-2 cm-3 Introduction: Physical properties • Mostly the hot phase of the Interstellar medium • High volume filling factor: f ~ 0.5 • Low density: np  10-2/-3 cm-3 • High temperature: T  106 K • Typical sizes: DOBa 100 pc, DSB  500 pc

  5. Super-bubble evolution: introduction • Superbubble = Collective interaction of multiple stellar winds (SW) and supernova (SN) explosions [MacLow & MacCray ’88] • t < 3-5 Myrs: SW merge  hot, low density cavity surrounded by a cold shell (swept-up ISM).  The “superwind bubble” model reproduces the gross morphological properties of SB well. • t > 3-5 Myrs: SN explode  large hole in the ISM. Continuous energy injection over 50 Myrs.

  6. Some difficulties:  usually overpredict SB size / observations [Smith & Wang ’04]  Other effects: radiative losses, magnetic field, density gradients, Coriolis forces, turbulence [review by Zaninetti’06] • Stellar contents (massive stars) & SN explosion  High metallicity (> Zsun up to 10 x Zsun) Metallicity: fraction in mass or number of atoms heavier than He. Ex; Sun: X(H)=0.8, Y(He)=0.18, Z(metals)=0.02

  7. The supershell • The supershell = the wall of a SB (or interacting clouds) in snowplough expansion (see Lecture I) • Produced rapidly at t > a few 104 yrs [Cioffi et al’88] - Number of stars N* = Ek/f ESN = 100 Ek,52/(f/0.1) ESN,51  If Ek > 1052 ergs N* > 100 ! [Heiles ’79] - density 102/3 cm-3 - To 10 to a few 100 K - metallicity Z a few Zsolar (early injection of metals by young stars [Perna & Raymond ’00] - Magnetic field up to 10Gauss (?), field swept-up by SN and stellar winds.

  8. Galaxy map MacClure-Griffiths et al ‘02 See review: Elherlova & Palous ‘05 3 well-known SB: Cygnus Orion-Eridanus Scorpius-Centaurus HI 21 cm line survey Shells  Interarm regions.

  9. Extragalactic SB • Magellanic Clouds (at ~ 50 kpc): • Doradus 30, biggest extragalactic HII region, R136 a young star clusters ionising flux= x 50 Orion; N175B: SNr, Doradus C: 2nd SB, SN1987A ….. Townsley et al ’06, Chandra 120pc x 120pc • Starburst galaxies: NGC253 central activity powered by multiple SB

  10. Why SB are important for CR physics ? • Sources of the Galactic cosmic rays (GCR), possibly with isolated SNr. • Sites of light nuclei nucleosynthesis Li-Be-B  Spallation gamma-ray lines. • Sources of gamma-rays  Targets for Tcherenkov telescopes, X-gamma-ray satellites (like XMM-newton, Chandra, Suzaku, Integral, Agile, GLAST). Linkbetween stellar formation, supernova production, interstellar turbulence and cosmic rays.

  11. Outlines • OB association (OBa) and Super-bubbles (SB) • Multi-wavelength observation of galactic and extragalactic OBa/SB • Massive stars clusters • Supernovæ in Super-bubbles • Turbulent SB • SB as cosmic-ray sources • SB as high energy sources • Conclusions

  12. Galactic & Extragalactic OBa/SB • A multi-wavelength survey.

  13. Real observational difficulty to investigate galactic SB - High extinction (optical, UV, X-rays) - Distances uncertainties (see for instance Cygnus) Uyaniker et al’01 The whole structure is itself composed by several bubbles. Finder chart for the Cygnus region in Galactic coordinates. Thick dashed-dotted ellipse: location of the SB; solid ellipses: approximate position and extent of the OB associations. Thick dashed lines: boundaries of the radio loops Dotted circles: prominent H II regions. Thin line contours: 3/4 keV ROSAT image  Observations of LMC & SMC

  14. Cold neutral shell • Neutral Hydrogen: 21cm line produced by collision of neutral ISM hydrogen (spin flip). • Molecular gas: CO mm rotational lines (ex, [1-0] at 2.3 mm) • Supershell structures in the Galaxy [Maciejewki et al’96, Ehlerova & Palous ‘05]  shell kinematics  kinetic energy  test the evolution models.

  15. Warm ionised ISM • Optical lines H, [OIII], [SII] To ~ 104K UV photons (OB stars, E>13.6eV) + H  H+ + e- e- + e-  heating mechanism e- + H, He, O, S  H,  recombinaison lines OIII, SII forbidden lines • UV lines CIV, SiIV, NV, To~105K

  16. Warm ionised medium II • Supersonic (shocks) motions inside HII (warm ionised) regions [Chu & Kennicut ’86, ‘94] • cs (WIM) ~ 10-30 km/s • Optical H,[OIII] line width  v ~ 100-200 km/s • shock acceleration  non-thermal radio emission.

  17. Hot ionised ISM (T > 106K) • Soft X-rays (Thermal Bremsstrahlung) observed by Rosat, Chandra, XMM-Newton • X-ray lines: - atomic lines (O to Fe) K,L,M transition. • Non-thermal X-rays (see next).

  18. 1 E in keV Chandra observations of Dor30 • Different components: • Diffuse X-rays • Composite SNr N157B • Cluster R136 Townsley et al ’06 • Thermal spectrum T~ 0.6 keV • ~ 90% of the X-ray Luminosity • Solar abundances

  19. Galactic clusters of massive stars in interaction Townsley et al ‘03

  20. Multi-wavelength images (Dor30) Red: Spitzer (6.5-9.4m): warm dust; Green: H (warm ISM) ; Blue: Chandra (0.9-2.3keV; hot ISM)

  21. Non-thermal emission • Radio • X-rays • Gamma-rays

  22. Non-thermal radio • SN remnants (see next and lecture I)

  23. 1 E (keV) Non-thermal X-rays • Point sources inside SB[Townsley et al’06: Dor30] • <10 % of the total X-ray luminosity • Non-thermal component with <> = 1.8  Emission dominated by one source Melnik34: WR colliding winds

  24. Non-thermal X-rays II • NT in the SB shell ? [Bamba et al’04 - Dor30c ] • Shell C &D : Dor30c • C = 2.3  0.2 ; D = 2.5  0.2 • Good correlation with a radio survey at 847 MHz [Mills et al’84] • “Consistent” with synchrotron radiation (extrapolation from radio, similarity with SN1006). • LXNT ~ 3x1035 erg/s~ 10 x LXNT(SN1006) •  Contribution from multiple SN ?

  25. LH54 Non-thermal X-rays III [Cooper et al’04]XMM-Newton observations of the SB DEML192 in the LMC. • Diffuse NT X-ray • emission (point stellar sources removed) - Integrated flux (cts-1) (1-3.5keV) = 1.3 ± 0.2 1-3.5 keV map. Contours: 3 & 6 above the background.

  26. NT X-rays: in our galaxy NGC 6634, NGC 2024 [Ezoe ’06] NGC2024

  27. Gamma-rays • Radioactive decay • Hegra source in CygOB2 • HESS (inner galaxy, galactic ridge surveys)

  28. 26Al  26Mg (1809 keV). • Cygnus X region observed by INTEGRAL: localised emission (massive star clusters at vrad ~ 0 km s-1) • Expanding shell / bubble of 26Al ? Radioactive decay 26Al E0 = 1808.4 ± 0.3 keV , vrad = -41 ± 50 km s-1 compatible with the SC velocity FWHM = 2.0 - 4.6 keV v = 330 - 760 km s-1 expansion velocities thin shell, radius 180-410 pc homologously expanding bubble, radius 260-590 pc

  29. TeV J2032+4130 an unidentified TeV source • TeV source in Cygnus OB2 SB •  = 1.9 0.3stat0.3sys • F(>1TeV) ~ 3% Crab • Extended source ~ 2 pc  No obvious counterpart (Chandra, Butt et al’06) • Wind interaction ? • Jet termination shock ? Skymap of excess events: 95% error ellipses of various EGRET sources, the core of Cygnus OB2, the location of Cyg X3. ASCA contours (2-10 keV) are overlayed [Aharonian et al’02]

  30. Milagro: diffuse Gamma-rays • Report of TeV diffuse emission from the Cygnus region [Smith et al’05] !only a proceedings. • 4.5 yrs of data • High significance signal ~ 2 Crab above 3 TeV. • Very extended ~ 5o across. • 7 unidentified Egret sources spatially coincident with highest significance point.

  31. HESS galactic unidentified sources • About a handful number of sources with no firm counterpart in galactic survey [Aharonian et al ’06] • HESS1813-178 • - Within 10’ from W33 • Complex; association with • a HII region with recent • star formation ? • - PWN ? • - =2.090.08 Theta square cut: slightly Extended source.

  32. Conclusion • SFR & SB observed from radio to gamma-rays. • Recent important progress: high spatial resolution instruments  mapping the different ISM phases. • Central stellar cluster  Lbol Evidences for supersonic motions • NT diffuse emission (X-rays, gamma-rays ?)

  33. Outlines • OB association (OBa) and Super-bubbles (SB) • Multi-wavelength observation of galactic and extragalactic OBa/SB • Massive stars clusters • Supernovæ in Super-bubbles • Turbulent SB • SB as cosmic-ray sources • SB as high energy sources • Conclusions

  34. Clusters of massive stars (young stellar clusters) • Different types of massive stars (O stars, Wolf-rayet). • Fraction of massive stars in OB association. • Stellar bubbles.  Main properties of a stellar cluster.

  35. Types of massive stars "live fast and die young.“ • O stars: The most luminous main sequence stars. • Produce the heavy elements via CNO cycle, He burning • - Mass > ~ 10 solar masses, Teff = 3x104K [Sun: 5800K] • - Lifetime of a few 106year [1010 yr] • - strong stellar winds, radiative pressure induced [weak stellar winds/induced by corona expansion] • - V  3000 km/s [300 km/s] • - high mass loss rates: 10-6 solar mass/year [10-14]

  36. HST: WR124 Wolf-Rayet stars • Wolf-Rayet stars: (descendants of very massive stars M>20 s.m.) - very short lifetime < 106 year  rare objects. - very high mass loss rate  10-5 solar mass/year - no H envelope - type of emission lines  Type of WR: WC, WN … • MS & WR winds are enriched in metals (C,N,O..)

  37. OB runaways • Some massive stars can escape the stellar cluster: - received a kick during a SN explosion. - expelled via dynamical encounters. • Fraction of OB runaways: (V > 30 km/s) - 20% O stars ; 5% B stars  A large Majority of OB stars: <V> ~ 4km/s do not travel by more than 120 pc during their lifetime. • Among the O runaways only a minority (~ 40%) are associated with a bow shock  moving in a hot (high sound speed) medium [Van Buren ’95, Huthoff & Kaper 02] • ~90% of the O stars can be associated with an OBa [Higdon& Lingenfelter ’06]

  38. One important issue • A majority of massive stars are born and die in their stellar cluster: From 60 % [Garmany ’94]to 85 % [Higdon & Lingenfelter ’06]. • A majority (about 90%) of Supernova are of type II [van den Bergh & Mc Clure ‘94] A majority of type II SN occur in the OB associations. Also a majority of type Ia [Higdon & Lingenfelter ’06]  85%  10%

  39. Stellar associations • Mean distances between two massive stars:  Each star occupies a radius R* = D*/2 ~ 6 pc. Hierachical star formationproduces sub-groups; D* may be smaller. Obs. Sco-Cen OB2, Orion [de Geus et al ’89, Brown et al ’94] or the starburst region 30 Doradus (LMC) [Walborn et al ’99]

  40. Cluste R136 in Doradus 30: - young cluster (age < 3 Myrs) - About 20 X-ray sources within few arcseconds: WR, WR/O systems  colliding winds. Portegies-Zwart et al’02

  41. L ~ 1051 ph s-1 ~ 100 O stars 104 - 105 Msol up to 100 such objects in our Galaxy (van den Bergh & Lafontaine 1984; Knödlseder et al. 2002) Galactic superstar clusters Arches Westerlund 1 + GC, W43, W49A, ... Cygnus OB2 Quintuplet

  42. Ambient ISM (ionised-HII region over ~ 60 pc) Shocked ISM (c) Shocked Stellar wind (b) Stellar wind 5pc 30pc Rs1 Rcd Rs2 O7 star @ 1 Myr in standard ISM Stellar wind bubbles I • Stellar wind bubble dynamics [Castor et al. ’75, Weaver et al. ’77] • Same phases as a SNr (lect I): free expansion-adiabatic- snowplough. • The snowplough phase starts at t >103 yrs and lasts over most of the star lifetime (a few Myrs).

  43. Stellar wind bubbles II • Stellar wind  (add energy) Shocked wind region (b)  (pushes) shell (c) [Avedisova ’72] Region b Region c • Solution Rsh t3/5  = 0.88[Weaver et al.’77]

  44. Super stellar wind bubbles • Self-similar external shock evolution in a MC. • Rext > R* (radius occupied by a SW, 6 pc) by a factor of a few. Very early in the OB association lifetime, a hot rarefied wind bubble does form.

  45. Outlines • OB association (OBa) and Super-bubbles (SB) • Multi-wavelength observation of galactic and extragalactic OBa/SB • Massive stars clusters • Supernovæ inside Super-bubbles • Turbulent SB • SB as cosmic-ray sources • SB as high energy sources • Conclusions

  46. Supernovæ inside Super-bubbles • Time evolution • Observational signatures • Interaction with molecular clouds • Stellar winds in evolved SB : - Wind-wind & wind-cloud interaction. - Particle acceleration.

  47. SN phases inside a SB • Major differences: • Free expansion and Sedov phases do last on longer timescales: nSB ~ 10-3 nst • The SB are hot medium  high sound speed ( TSB1/2)  most of SN shocks become subsonic before entering the radiative phase.

  48. Observational signatures (?) • Any or a few !  But they are in ! as most of SNII occur in SB and SB expansion requires the SN mechanical energy !

  49. Observation of SN/SB • Three main ways: [Chu ’95] discriminate among HII/SB - HII high [SII]/H SB low [SII]/H - HII Non-thermal radio emission SB non radiation (ne is low) - X-ray emission of shocked gas ( > LX produced in the SW bubble model).

  50. SN in interaction with molecular clouds • SN exploding close to the parent MCs or at the SB edge: • Enter the radiative phase sooner (at smaller radii) [Chevalier ’99] • Detection through optical lines H , SII, OIII: shock (vs ~ 100 km/s): cloud interaction (n ~10 cm-3, T ~104-5K) [Bocchino et al ’00] + X-ray radiation from less dense regions. • NT particles expected  hard X-rays & gamma-rays (IC443, Gamma Cygni) [Bykov et al ’00, ‘04]

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