Presentation is loading. Please wait.

Presentation is loading. Please wait.

Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Fund. Physics & Astrophysics of Supernova Remnants Lecture #1 –What.

Similar presentations


Presentation on theme: "Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Fund. Physics & Astrophysics of Supernova Remnants Lecture #1 –What."— Presentation transcript:

1 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Fund. Physics & Astrophysics of Supernova Remnants Lecture #1 –What SNRs are and how are they observed –Hydrodynamic evolution on shell-type SNRs –Microphysics in SNRs – electron-ion equ Lecture #2 –Microphysics in SNRs - shock acceleration –Statistical issues about SNRs Lecture #3 –Pulsar wind nebulae

2 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Order-of magn. estimates SN explosion –Mechanical energy: –Ejected mass: VELOCITY: Ambient medium –Density: M ej ~M swept when: SIZE: AGE:

3 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Classical Radio SNRs Spectacular shell-like morphologies –compared to optical –polarization –spectral index ( ~ – 0.5 ) BUT Poor diagnostics on the physics –featureless spectra (synchrotron emission) –acceleration efficiencies ? Tycho – SN 1572

4 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 90cm Survey 4.5 < l < 22.0 deg (35 new SNRs found; Brogan et al. 2006 ) Blue: VLA 90cm Green: Bonn 11cm Red: MSX 8 m Radio traces both thermal and non-thermal emission Mid-infrared traces primarily warm thermal dust emission A view of Galactic Plane

5 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 SNRs in the X-ray window Probably the best spectral range to observe –Thermal: measurement of ambient density –Non-Thermal: synchrotron-emitting electrons are near the maximum energy (synchrotron cutoff)

6 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 X-ray spectral analysis Low-res data –Overall fit with thermal models High-res data –Abundances of elements –Single-line spectroscopy!

7 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Shell-type SNR evolution a classical (and wrong) scenario Isotropic explosion and further evolution Homogeneous ambient medium Three phases: Linear expansion Adiabatic expansion Radiative expansion Isotropic Homogeneous Linear Adiabatic Radiative

8 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Basic concepts of shocks Hydrodynamic (MHD) discontinuities Quantities conserved across the shock –Mass –Momentum –Energy –Entropy Jump conditions (Rankine-Hugoniot) Independent of the detailed physics shock V If Strong shock

9 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Density Radius Forward shock Reverse shock Forward and reverse shocks Forward Shock: into the CSM/ISM (fast) Reverse Shock: into the Ejecta (slow)

10 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Dimensional analysis and Self-similar models Dimensionality of a quantity: Dimensional constants of a problem –If only two, such that M can be eliminated, THEN evolution law follows immediately! Reduced, dimensionless diff. equations –Partial differential equations (in r and t ) then transform into total differential equations (in a self-similar coordinate).

11 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Early evolution Linear expansion only if ejecta behave as a piston Ejecta with and Ambient medium withand Dimensional parameters and Expansion law:

12 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 A self-similar model Deviations from linear expansion Radial profiles –Ambient medium –Forward shock –Contact discontinuity –Reverse shock –Expanding ejecta (Chevalier 1982)

13 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Evidence from SNe VLBI mapping (SN 1993J) Decelerated shock For an r -2 ambient profile ejecta profile is derived

14 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The Sedov-Taylor solution After the reverse shock has reached the center Middle-age SNRs –swept-up mass >> mass of ejecta –radiative losses are negligible Dimensional parameters of the problem Evolution: Self-similar, analytic solution (Sedov,1959)

15 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The Sedov profiles Most of the mass is confined in a thin shell Kinetic energy is also confined in that shell Most of the internal energy in the cavity Density Temperature Pressure

16 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Thin-layer approximation Layer thickness Total energy Dynamics Correct value: 1.15 !!!

17 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 What can be measured (X-rays) from spectral fits … if in the Sedov phase

18 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 SN 1006 Dec.Par. = 0.34 Tycho SNR (SN 1572) Dec.Par. = 0.47 Testing Sedov expansion Required: R SNR /D (angular size) t (reliable only for historical SNRs) V exp /D (expansion rate, measurable only in young SNRs) Deceleration parameter

19 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Other ways to measure the shock speed Radial velocities from high-res spectra (in optical, but now feasible also in X-rays) Electron temperature from modelling the (thermal) X-ray spectrum Modelling the Balmer line profile in non- radiative shocks (see below)

20 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 End of the Sedov phase Sedov in numbers: When forward shock becomes radiative: with Numerically:

21 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Beyond the Sedov phase When t>t tr, energy no longer conserved. What is left? Momentum-conserving snowplow (Oort 1951) WRONG !! Rarefied gas in the inner regions Pressure-driven snowplow (McKee & Ostriker 1977) Kinetic energy Internal energy

22 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Numerical results t tr Blondin et al 1998 2/5 0.33 2/7=0.291/4=0.25 (Blondin et al 1998)

23 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 An analytic model Thin shell approximation Analytic solution H either positive(fast branch) limit case: Oort or negative (slow branch) limit case: McKee & Ostriker H, K from initial conditions Bandiera & Petruk 2004

24 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Inhomogenous ambient medium Circumstellar bubble ( ρ ~ r -2 ) –evacuated region around the star –SNR may look older than it really is Large-scale inhomogeneities –ISM density gradients Small-scale inhomogeneities –Quasi-stationary clumps (in optical) in young SNRs (engulfed by secondary shocks) –Thermal filled-center SNRs as possibly due to the presence of a clumpy medium

25 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Collisionless shocks Coulomb mean free path –Collisional scale length (order of parsecs) –Larmor radius is much smaller (order of km) High Mach numbers –Mach number of order of 100 MHD Shocks –B in the range 10-100 μG Complex related microphysics –Electron-ion temperature equilibration –Diffusive particle acceleration –Magnetic field turbulent amplification

26 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Electron & Ion equilibration Naif prediction, for collisionless shocks But plasma turbulence may lead electrons and ion to near-equilibrium conditions Coulomb equilibration on much longer scales (Cargill and Papadopoulos 1988) (Spitzer 1978)

27 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Optical emission in SN1006 Pure Balmer emission in SN 1006 Here metal lines are missing (while they dominate in recombination spectra) –Extremely metal deficient ?

28 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Non-radiative emission Emission from a radiative shock: –Plasma is heated and strongly ionized –Then it efficiently cools and recombines –Lines from ions at various ionization levels In a non-radiative shock: –Cooling times much longer than SNR age –Once a species is ionized, recombination is a very slow process WHY BALMER LINES ARE PRESENT ?

29 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The role of neutral H Scenario: shock in a partially neutral gas Neutrals, not affected by the magnetic field, freely enter the downstream region Neutrals are subject to: –Ionization (rad + coll) [LOST] –Excitation (rad + coll) Balmer narrow –Charge exchange (in excited lev.) Balmer broad (Chevalier & Raymond 1978, Chevalier, Kirshner and Raymond 1980) Charge-exchange cross section is larger at lower v rel Fast neutral component more prominent in slower shocks

30 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 H-alpha profiles (Hester, Raymond and Blair 1994) (Kirshner, Winkler and Chevalier 1987) Cygnus Loop FWHM of broad component ( T i !!) FWHM of narrow component ( T 40,000 K – why not fully ionized?) MEASURABLE QUANTITIES Intensity ratio Displacement (not if edge-on)

31 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 SNR 1E 0102.2-7219 Very young and bright SNR in the SMC Expansion velocity ( 6000 km s -1, if linear expansion) measured in optical (OIII spectra) and in X-rays (proper motions) Electron temperature ~ 0.4-1.0 keV, while expected ion T ~ 45 keV Very small T e /T i, or T i much less than expected? Missing energy in CRs? (Hughes et al 2000, Gaetz et al 2000) Optical Radio X-rays

32 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007

33 Lectures #2 & #3 Shock acceleration –The prototype: SN 1006 –Physics of shock acceleration –Efficient acceleration and modified shocks Pulsar Wind Nebulae –The prototype: the Crab Nebula –Models of Pulsar Wind Nebulae –Morphology of PWN in theory and in practice –A tribute to ALMA

34 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The strange case of SN1006 Tycho with ASCA Hwang et al 1998 Standard X-ray spectrum

35 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Thermal & non-thermal Power-law spectrum at the rims Thermal spectrum in the interior

36 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 shock X flow speed (in the shock reference frame) Diffusive shock acceleration Fermi acceleration –Converging flows –Particle diffusion (How possible, in a collisionless plasma?) Particle momentum distribution where r is the compression ratio ( s=2, if r = 4 ) Synchrotron spectrum For r = 4, power-law index of -0.5 Irrespectively of diffusion coefficient

37 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The diffusion coefficient Diffusion mean free path (magnetic turbulence) (η > 1) Diffusion coefficient

38 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 …and its effects Acceleration time Maximum energy Cut-off frequency –Naturally located near the X-ray range –Independent of B

39 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Basics of synchrotron emission Emitted power Characteristic frequency Power-law particle distribution Ifthen Synchrotron life time

40 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 SN 1006 spectrum Rather standard ( -0.6 ) power-law spectrum in radio (-0.5 for a classical strong shock) Synchrotron X-rays below radio extrapolation Common effect in SNRs (Reynolds and Keohane 1999) Electron energy distribution: Fit power-law + cutoff to spectrum: Rolloff frequency

41 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Measures of rolloff frequency SN 1006 (Rothenflug et al 2004) Azimuthal depencence of the break Changes in t acc ? or in t syn ? η of order of unity?

42 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Dependence on B orientation? Highly regular structure of SN 1006. Barrel-like shape suggested (Reynolds 1998) Brighter where B is perpendicular to the shock velocity? Direction of B ?

43 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Radio – X-ray comparison Similar pattern (both synchrotron) Much sharper limb in X-rays (synchrotron losses) (Rothenflug et al 2004)

44 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 (Rothenflug et al 2004) Evidence for synchrotron losses of X-ray emitting electrons X-ray radial profile INCONSISTENT with barrel-shaped geometry (too faint at the center)

45 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 3-D Geometry. Polar Caps? Ordered magnetic field (from radio polarization) Polar cap geometry: electrons accelerated in regions with quasi-parallel field (as expected from the theory)

46 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Statistical analysis (Fulbright & Reynolds 1990) Barrel-like SNR (under various orientations) Polar cap SNR (under various orientations) Expected morphologies in radio

47 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The strength of B ? Difficult to directly evaluate the value of the B in the acceleration zone. ν rolloff is independent of it ! Measurements of B must rely on some model or assumption

48 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Very sharp limbs in SN 1006 ASCA Chandra

49 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 B from limb sharpness Profiles of resolved non-thermal X-ray filaments in the NE shell of SN 1006 (Bamba et al 2004) Length scales 1 (0.01 pc) upstream 20 (0.19 pc) downstream Consistent with B ~ 30 μG

50 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 A diagnostic diagram Acceleration time t acc = 270 yr Derivation of the diffusion coefficients: u =8.9 10 24 cm 2 s -1 d =4.2 10 25 cm 2 s -1 (U s =2900 km s -1 ) to compare with Bohm =(E max c/eB)/3 rolloff t sync > t acc > Bohm

51 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Non-linear shock acceleration Such high values of B are not expected in the case of pure field compression ( 3-6 μG in the ISM, 10-20 μG in the shock – or even no compression in parallel shocks) Turbulent amplification of the field? Possible in the case of efficient shock acceleration scenario: particles, streaming upstream, excite turbulence (e.g. Berezhko; Ellison; Blasi)

52 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Shock modification Dynamical effects of the accelerated particles onto the shock structure (Drury and Voelk 1981) Intrinsically non linear Shock precursor Discontinuity (subshock) Larger overall compression factor Accelerated particle distribution is no longer a power-law

53 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Deviations from Power-Law In modified shocks, acc. particles with different energies see different shock compression factors. Higher energy Longer mean free path Larger compress.factor Harder spectrum Concavity in particle distribution. (also for electrons) Standard PL Thermal Blasi Solution

54 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Gamma-ray emission Measurement of gamma-ray emission, produced by the same electrons that emit X-ray synchrotron, would allow one to determine the value of B. Synchrotron IC Radio X-ray γ-ray νFννFν

55 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 On the other hand, there is another mechanism giving Gamma-ray emission –accelerated ions –p-p collisions –pion production –pion decay (gamma) Lower limit for B Need for targets (molecular cloud?) Efficiency in in accelerating ions? (The origin of Cosmic rays) (Ellison et al 2000)

56 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 TeV telescopes generation H.E.S.S. Cherenkov telescopes Observations : RX J0852.0-4622 (Aharonian et al 2005) Upper limits on SN 1006 (Aharonian et al 2005) RX J1713.7-3946 (Aharonian et al 2006)

57 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Observ. of RX J0852.0-4622 Good matching between X-rays and gamma-rays CO observation show the existence of a molecular cloud Pion-decay scenario slightly favoured. Nothing proved as yet

58 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Indirect tests on the CRs Some model-dependent side effects of efficient particle acceleration Forward and reverse shock are closer, as effect of the energy sink HD instabilities behavior depends on the value of eff (Decourchelle et al 2000) (Blondin and Ellison 2001)

59 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Shock acceleration efficiency Theory predicts (~ high) values of the efficiency of shock acceleration of ions. Little is known for electrons Main uncertainty is about the injection process for electrons –Shock thickness determined by the mfp of ions (scattering on magnetic turbulence) –Electrons, if with lower T, have shorter mfps –Therefore for them more difficult to be injected into the acceleration process

60 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The Σ–D Relationship Empirical relation –SNR surface brightness, in radio –SNR diameter –Any physical reason for this relation ? (Case & Bhattacharya 1998)

61 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 A basic question Is the correlation representative of the evolution of a typical object? Or is, instead, the convolution of the evolution of many different objects? Theorists attempts to reproduce it. Berezhko & Voelk 2004

62 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Dependence on ambient density Primary correlations are D-n, and Σ-n Diff. ISM conditions (Berkhuijsen 1986)

63 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007

64 Crab Nebula – H cont Crab Nebula - radio X-rays The Prototype The Crab Nebula Optical Thermal filaments Amorphous compon. Radio Filled-center nebula No signs of shell X-rays More compact neb. Jet-torus structure

65 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The Crab Nebula spectrum -0.3 -1.1 -0.8 -1.5 Synchrotron emission (apart from optical filaments and IR bump) Radio Optical Soft X-rays Hard X-rays

66 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Some basic points Synchrotron efficiency –10-20% of pulsar spin-down power Powered by the pulsar High polarizations (ordered field) No signs of any associated shell.

67 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Basics of synchrotron emission Emitted power Characteristic frequency Power-law particle distribution Ifthen Synchrotron life time

68 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Simple modelling Homogeneous models (no info on structure) Magnetic field evolution –Early phases (constant pulsar input) –Later phases (most energy released) (Pacini & Salvati 1973)

69 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Power-law injection –With upper energy cutoff –Continuum injection link to the pulsar spin down Particle evolution (adiabatic vs synchrotron losses) Evolutionary break Adiabatic regime (-0.3 in radio) Synchrotron-dominated regime (-0.8 in optical)

70 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Kennel & Coroniti model (1984) Basics of Pulsar Wind Nebula scenario Pulsar magnetosphere Pulsar wind Termination shock Pulsar Wind Nebula Interface with the ejecta (CD, FS) Stellar ejecta Interface with the ambient medium (RS, CD, FS) Ambient medium (either ISM or CSM) Pulsar magnetosphere Pulsar wind Termination shock Pulsar Wind Nebula Stellar ejecta ISM

71 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The ingredients Pulsar wind –super-relativistic –magnetized (toroidal field) –isotropic Termination shock –mass conservation –magnetic flux cons. –momentum cons. –energy cons. where(specific enthalpy)

72 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Large and small σ limits Large σ –weak shock –flow stays super-relativistic –neither field, nor density jump –inefficient in converting kinetic into thermal energy Small σ –strong shock –flow braked to mildly relativistic speed –both field and density increase –kinetic energy efficienly converted

73 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 MHD evolution in the nebula Steady solution (flow timescale << SNR age) –number flux cons.- magnetic flux cons. –momentum cons.- energy cons. Asymptotic velocity!!! –no solution for V =0 –outer expansion V ext ~1500 km s -1 (for the Crab Nebula) –then σ~3 10 -3 –size of termination shock, from balance of wind ram pressure and nebular pressure R n ~10 arcsec (wisps region)

74 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Radial profiles Inner part with: Outer part with: Equipartition in the outer part:

75 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Do we expect what observed? Injected particles –power-law, between a min and a max energy –only 1 free parameter ( n 2 and p 2 from the jump conditions at the termination shock) –plus wind parameters ( L, σ and γ 1 ) Energy evolution during radial advection

76 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Best-fit solution Parameters: Fit to:

77 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007

78 Problems -Ia The sigma paradox –A value is required, in order to get an effective slowing-down of the flow, and a high ( 10-20 % ) synchrotron conversion efficiency –BUT the (magnetically driven) pulsar wind cannot have been produced with a low σ. –With a normal MHD evolution, the value of σ must keep constant from the acceleration region till the termination shock.

79 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Problems - Ib A POSSIBLE WAY OUT –A tilted pulsar generates a striped wind.

80 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Problems -Ic –Magnetic reconnection in the wind zone (if possible) would dissipate the field. (Coroniti 1990) –Reconnection in the wind zone does not efficiently destroy the field. Reconnection at the termination shock is more effective. (Lyubarski & Kirk 1991)

81 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Problems - IIa The unexpected radio emission –Predicted radio flux is far lower (a factor ~100 ) than observed. –No easy way to cure it. Little freedom on the particle number. Total power is fixed: more particles mean a lower γ 1. –Radio emitting electrons as a relict. Was the Crab much more powerful in the past? Ad hoc. All PWNe are radio emitters.

82 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Problems IIb –Can it be Diffusive synchrotron radiation? (Fleishman & Bietenholz 2007) Turbulence spectral index ν. –Theory only for a fully turbulent field Total spectrum is reproduced But observed polarization is not explained

83 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Non-spherical structure Particle, moving passively along field lines (flow motion assumed to be irrotational) Axisymmetric nebular field structure Steady state solutions (Begelman & Li 1992)

84 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 van der Swaluw 2003 pulsar axis 3C 58 MHD simulations

85 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Elongated structures of PWNe G5.4-0.1 Crab Nebula pulsar spin G11.2-0.3 3C 58

86 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Details of the structure knot jet inner ring torus counter-jet Crab Nebula Vela

87 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Crab Nebula (Weisskopf et al 2000) 40 = 0.4 pc PSR B1509-58 (Gaensler et al 2002) 4 = 6 pc 3C 58 (Slane et al. 2004) 13 = 0.2 pc 80 = 0.8 pc Vela Pulsar (Pavlov et al. 2003) Jet sizes

88 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Simulating PWNe Relativistic MHD codes Modelling a PWN like the Crab Velocity Magnetization Max Energy (Komissarov, 2006; Del Zanna et al 2004, 2006)

89 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Surface brightness maps Jet-Torus structure

90 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Ingredients Wind parameters –magnetization (still small, but not too much) σ~0.02 – 0.1 aaa –wind anisotropy ( γ eq ~10 γ pol ) –filling the jets (since B = 0 )

91 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 ISM Shocked ISM Shocked EjectaUnshocked Ejecta PWN Pulsar Wind Forward Shock Reverse Shock PWN Shock Pulsar Termination Shock PWN-ejecta interaction PWNe are confined by the associated shell-like SNR Not only the SNR is detectable (like in the Crab) In the Crab Nebula UV emission associated with a slow shock (against the SN ejecta)

92 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007

93 A TRIBUTE TO ALMA SNRs and PWNs are mostly non-thermal in that spectral range. –no use of spectral capabilities –use of high spatial resolution, + wide field, + photometric stability (extended sources) Is mm-submm a new band for SNRs, or just an extension of the radio range? A study of the Crab Nebula (extension of a former work, Bandiera et al 2002 )

94 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 What has been done already Comparison of 1.3 mm (230 GHz) images (with IRAM 30-m telescope, 10 res) and radio (20 cm, VLA) maps 230 GHz map Spectral map -0.28 -0.20

95 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 A further emission component Radio spectral index: -0.27 Concave spectral index from radio to mm Real effect or artifact? (absolute photometry) Evidence for an additional emission component

96 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Component B Image obtained optimizing the subtraction of amorphous part, and filaments, of radio image (PSF matched), with best-fit weights.

97 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The subtracted components Amorphous component: consistent with an extension of the spectrum to mm, with the radio spectral index (-0.27). Filaments: consistent with spectral bending ( ν b ~80 GHz ). Morphologically, component B resembles more the Crab in the optical than in the radio (ALTHOUGH, in the mm range, electrons of Component B do not lose energy significantly by synchrotron).

98 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 The integrated spectrum Radio comp (A) Component B, with low freq cutoff. Evidence higher than from the error bar. Components A and B coexist in the optical.

99 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Physical scenario Number of particles in Component B: N tot ~ 2 10 48. Consistent with Kennel & Coroniti) Filament magnetic fields ~6 times higher than the rest AND particle do not diffuse in/out of filaments (κ<100 κ B ).

100 Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 With ALMA The same analysis, with a resolution 100 times higher. Detailed mapping of Component B. Separation of comp A and B also through differences in the polarization patterns. Analysis of the spectral bending in individual filaments, and possibly even across the filament (B estimates). Mapping B in filaments (aligned? ordered?)


Download ppt "Rino Bandiera, OAAFundamental Physics & Astrophysics of SNRsSNA07, May 20-26, 2007 Fund. Physics & Astrophysics of Supernova Remnants Lecture #1 –What."

Similar presentations


Ads by Google