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Structure and Evolution

Structure and Evolution. of Pulsar Wind Nebulae. Take In:. Pulsars are born as reservoirs of tremendous rotational energy Their strong magnetic fields and rapid rotation rates promote loss of rotational energy through formation of a relativistic magnetized wind

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Structure and Evolution

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  1. Structure and Evolution of Pulsar Wind Nebulae Patrick Slane MODE SNR/PWN Workshop

  2. Take In: • Pulsars are born as reservoirs of tremendous rotational energy • Their strong magnetic fields and rapid rotation rates promote loss of • rotational energy through formation of a relativistic magnetized wind • Particles from that wind eventually merge into the ISM. Pulsars thus • convert rotational energy into diffuse relativistic particle energy in the ISM How can we possibly follow the conversion of a rotational energy exceeding 1031 erg cm-3 to its ultimate fate as a particle energy density comprising a tiny fraction of 1 eV cm-3? (Hint: It isn’t easy, and still far from perfect…) Patrick Slane MODE SNR/PWN Workshop

  3. Jet/Torus Structure in PWNe • Anisotropic flux with • maximum energy flux • in equatorial zone • - radial particle outflow • - striped wind from • Poynting flux • decreases away • from equator • - Wind in nebula is • particle-dominated van den Heuvel 2006 Patrick Slane MODE SNR/PWN Workshop

  4. Jet/Torus Structure in PWNe • Anisotropic flux with • maximum energy flux • in equatorial zone • - radial particle outflow • - striped wind from • Poynting flux • decreases away • from equator • - Wind in nebula is • particle-dominated Lyubarsky 2002 Patrick Slane MODE SNR/PWN Workshop

  5. Jet/Torus Structure in PWNe Crab • Polar jets form • - subject to kink • instabilities • - outflow speeds > 0.2c • (e.g. Gaensler et al. 2002) • Anisotropic flux with • maximum energy flux • in equatorial zone • - radial particle outflow • - striped wind from • Poynting flux • decreases away • from equator • - Wind in nebula is • particle-dominated • - Doppler beaming • indicates torus flows • with v > 0.4c (e.g., Lu • et al. 2001) Seward et al. 2006 G54.1+0.3 Lu et al. 2001 Vela Patrick Slane MODE SNR/PWN Workshop Pavlov et al. 2003

  6. Jet/Torus Structure in PWNe Crab • Polar jets form • - subject to kink • instabilities • - outflow speeds > 0.2c • (e.g. Gaensler et al. 2002) • Anisotropic flux with • maximum energy flux • in equatorial zone • - radial particle outflow • - striped wind from • Poynting flux • decreases away • from equator • - Wind in nebula is • particle-dominated • - Doppler beaming • indicates torus flows • with v > 0.4c (e.g., Lu • et al. 2001) Seward et al. 2006 G54.1+0.3 pulsar axis Begelman & Li 1992 Lu et al. 2001 3C 58 • Magnetic tension in • equatorial plane results • in elongation along • rotation axis Slane et al. 2004 Patrick Slane MODE SNR/PWN Workshop

  7. Jet/Torus Structure in PWNe Crab • Polar jets form • - subject to kink • instabilities • - outflow speeds > 0.2c • (e.g. Gaensler et al. 2002) • Anisotropic flux with • maximum energy flux • in equatorial zone • - radial particle outflow • - striped wind from • Poynting flux • decreases away • from equator • - Wind in nebula is • particle-dominated • - Doppler beaming • indicates torus flows • with v > 0.4c (e.g., Lu • et al. 2001) Hester et al. 2008 G54.1+0.3 pulsar axis Begelman & Li 1992 Lu et al. 2001 3C 58 • Magnetic tension in • equatorial plane results • in elongation along • rotation axis Slane et al. 2004 Patrick Slane MODE SNR/PWN Workshop

  8. PWNe and Their SNRs Reverse Shock PWN Shock Forward Shock Pulsar Termination Shock Pulsar Wind Unshocked Ejecta Shocked Ejecta Shocked ISM PWN ISM • Pulsar • - injects particles and Poynting flux • Pulsar Wind • - sweeps up ejecta; shock decelerates • flow, accelerates particles; PWN forms • Supernova Remnant • - sweeps up ISM; reverse shock heats • ejecta; ultimately compresses PWN; energy distribution of particles in nebula tracks • evolution; instabilities at PWN/ejecta interface may allow particle escape Gaensler & Slane 2006 Patrick Slane MODE SNR/PWN Workshop

  9. Example: G292.0+1.8 Park et al. 2007 Red: O Lya, Ne Hea Orange: Ne Lya Green: Mg Hea Blue: Si Hea, S Hea 4.0-7.0 keV Chandra/ACIS Patrick Slane MODE SNR/PWN Workshop

  10. Example: G292.0+1.8 Park et al. 2007 Red: O Lya, Ne Hea Orange: Ne Lya Green: Mg Hea Blue: Si Hea, S Hea Lee et al. 2010 Chandra/ACIS • X-rays reveal shocked wind from • massive progenitor star Patrick Slane MODE SNR/PWN Workshop

  11. PWN Evolution see Gelfand et al. 2009 energy input and swept-up ejecta mass PWN evolution Patrick Slane MODE SNR/PWN Workshop

  12. PWN Evolution energy input and swept-up ejecta mass Vorster et al. 2013 PWN evolution Patrick Slane MODE SNR/PWN Workshop

  13. Evolution of PWN Emission • Spin-down power is injected into the • PWN at a time-dependent rate • Assume input spectrum (e.g., PL): • - note that studies of Crab and other • PWNe suggest that there may be • multiple components • Get associated synchrotron and IC emission from electron population in the • evolved nebula • - combined information on observed spectrum and system size provide • constraints on underlying structure and evolution Patrick Slane MODE SNR/PWN Workshop

  14. Evolution of PWN Emission • Spin-down power is injected into the • PWN at a time-dependent rate • Assume input spectrum (e.g., PL): • - note that studies of Crab and other • PWNe suggest that there may be • multiple components • Get associated synchrotron and IC emission from electron population in the • evolved nebula • - combined information on observed spectrum and system size provide • constraints on underlying structure and evolution Patrick Slane MODE SNR/PWN Workshop

  15. Evolution of PWN Emission • Spin-down power is injected into the • PWN at a time-dependent rate • Assume input spectrum (e.g., PL): • - note that studies of Crab and other • PWNe suggest that there may be • multiple components 1000 yr 2000 yr 5000 yr CMB inverse Compton synchrotron • Get associated synchrotron and IC emission from electron population in the • evolved nebula • - combined information on observed spectrum and system size provide • constraints on underlying structure and evolution Patrick Slane MODE SNR/PWN Workshop

  16. Injection from Relativistic Shocks Spitkovsky 2008 • PIC simulations of particle acceleration in relativistic shocks show build-up • of energetic particles (Spitkovsky 2008) • Multi-component input spectrum: Maxwellian + power law • – and possibly more complex if conditions differ at different acceleration sites Patrick Slane MODE SNR/PWN Workshop

  17. PWN Structure & Evolution: 3C 58 Slane et al. 2008 Slane et al. 2004 • Thermal X-rays evident from shocked ejecta • (Bocchino et al. 2001; Slane et al. 2004) • Spectrum of torus indicates complex injection • spectrum (Slane et al. 2008) • - evidence of position-dependent acceleration? Patrick Slane MODE SNR/PWN Workshop

  18. PWN Structure & Evolution: SNR 0540-69 • Multi-l studies reveal 0-rich ejecta, • bright PWN, young pulsar, expanding • SNR shell • Broadband spectrum shows evolutionary • break • - disconnect in X-rays complicates • interpretation; may indicate complex • injection spectrum CXO Kaaret et al. 2001 Mignani et al. 2012 Patrick Slane MODE SNR/PWN Workshop

  19. Matheson & Safi-Harb 2005 CXO G21.5-0.9 • X-rays reveal SNR shell and PWN with • compact core and (Slane et al. 2000) • - shell from dust scattering, DSA, and • ejecta (Bocchino et al. 2005) • - radio observations identify young, faint • pulsar (Camilo et al. 2006) 36 arcsec Patrick Slane MODE SNR/PWN Workshop

  20. Matheson & Safi-Harb 2005 CXO G21.5-0.9 • X-rays reveal SNR shell and PWN with • compact core and (Slane et al. 2000) • - shell from dust scattering, DSA, and • ejecta (Bocchino et al. 2005) • - radio observations identify young, faint • pulsar (Camilo et al. 2006) • PWN and torus detected in IR • - Broadband spectrum of torus shows • evidence of structure between IR and X-ray Spitzer 24/8 mm Patrick Slane MODE SNR/PWN Workshop

  21. G21.5-0.9 • X-rays reveal SNR shell and PWN with • compact core and (Slane et al. 2000) • - shell from dust scattering, DSA, and • ejecta (Bocchino et al. 2005) • - radio observations identify young, faint • pulsar (Camilo et al. 2006) • PWN and torus detected in IR • - Broadband spectrum of torus shows • evidence of structure between IR and X-ray • [Fe II] 1.64 mm image shows shocked • ejecta surrounding PWN • Polarization in IR indicates magnetic field • with toroidal geometry [Fe II] 1.64 mm Zajczyk et al. 2012 Ks linear-polarized intensity Patrick Slane MODE SNR/PWN Workshop

  22. RS Interactions: G327.1-1.1 • G327.1-1.1 is a composite SNR • for which radio morphology • suggests PWN/RS interaction t = 20,000 yr high r low r Blondin et al. 2001 Patrick Slane MODE SNR/PWN Workshop Temim et al. 2009

  23. prings RS Interactions: G327.1-1.1 prongs cometary structure tail pulsar + torus? Patrick Slane MODE SNR/PWN Workshop Temim et al. 2009

  24. RS Interactions: G327.1-1.1 prongs cometary structure tail pulsar + torus? Radio Simulation Patrick Slane MODE SNR/PWN Workshop Temim et al. 2009

  25. RS Interactions: MSH 15-56 Temim et al. 2013 • Radio observations reveal shell with • bright, flat-spectrum nebula in center • - no pulsar known, but surely a PWN • - nebula significantly displaced from SNR • center • X-ray studies show thermal shell w/ • very faint hard emission near PWN • - pulsar candidate seen as hard point source • w/ faint X-ray trail extending to PWN Patrick Slane MODE SNR/PWN Workshop

  26. RS Interactions: MSH 15-56 Temim et al. 2013 • Radio observations reveal shell with • bright, flat-spectrum nebula in center • - no pulsar known, but surely a PWN • - nebula significantly displaced from SNR • center Patrick Slane MODE SNR/PWN Workshop

  27. RS Interactions: MSH 15-56 • X-ray spectrum gives n0 ≈ 0.1 cm-3 • SNR/PWN modeling gives t ≈ 12 kyr • - SNR reverse shock has completely • disrupted PWN • Fermi observations of MSH 15-56 may • be consistent with emission from an • evolved PWN • - if correct, pulsar has essentially departed • relic PWN and is injecting particles into • newly-forming nebula • - additional observations required to better • constrain ambient density and ejecta mass Temim et al. 2013 Patrick Slane MODE SNR/PWN Workshop

  28. Vela X: An Evolved PWN LaMassa et al. 2008 de Jager et al. 2008 pulsar wind ejecta cocoon pulsar Radio PWN Patrick Slane MODE SNR/PWN Workshop

  29. Vela X: An Evolved PWN • TeV emission observed concentrated • along cocoon • - GeV emission observed throughout • PWN, but brightest region is offset • from TeV peak Fermi LAT contours Hinton et al. 2011 H.E.S.S. contours • TeV peak may be recent injection into • cocoon following RS interaction • - older energetic particles may have • been lost to diffusion; however… Patrick Slane MODE SNR/PWN Workshop

  30. Vela X: An Evolved PWN hard emission at Fermi LAT peak Fermi LAT contours H.E.S.S. contours Re-acceleration of low energy electrons, producing GeV IC peak and flat X-ray spectrum? nonthermal emission hard along cocoon, but soft in eastern PWN as expected from synchrotron losses Patrick Slane MODE SNR/PWN Workshop

  31. Take Away • Pulsars are born as reservoirs of tremendous rotational energy • Their strong magnetic fields and rapid rotation rates promote loss of • rotational energy through formation of a relativistic magnetized wind • Particles from that wind eventually merge into the ISM. Pulsars thus • convert rotational energy into diffuse relativistic particle energy in the ISM • The magnetic/particle pulsar wind is axisymmetric and particle-dominated. • It creates a nebula that drives itself through the interior of its host SNR. • - The particle spectrum is complicated. This affects the multi-l spectrum. • The evolution of the wind nebula is strongly affected by that of its surrounding • SNR, particularly the mass of its ejecta, and the density of its surroundings. • - Early evolution can be dominated by massive radiative losses. Late evolution • can be dominated by asymmetric crushing of nebula. This may increase • diffusive escape of particles. • Our models for PWN evolution can be directly tied to phenomena that we • can image, and spectral evolution that we can resolve. The picture is still • evolving, but we are clearly on the right track. Patrick Slane MODE SNR/PWN Workshop

  32. Summary • Multiwavelength studies of PWNe reveal: • - spin properties of central engines • - geometry of systems • - spatially-resolved spectra • - interaction with supernova ejecta • - presence of freshly-formed dust • These lead to constraints on: • - particle acceleration in relativistic shocks • - formation of jets • - physics of pulsar magnetospheres • - nature of progenitor stars • - early and late-phase evolution of pulsar winds • Current advances are being made across the electromagnetic spectrum, • as well as in theoretical modeling, and point the way for investigations • in virtually every wavelength band. Patrick Slane MODE SNR/PWN Workshop

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