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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
Structure and Evolution

of Pulsar Wind Nebulae

Patrick Slane MODE SNR/PWN Workshop

take in
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

jet torus structure in pwne
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

jet torus structure in pwne1
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

jet torus structure in pwne2
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

jet torus structure in pwne3
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

jet torus structure in pwne4
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

pwne and their snrs
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

example g292 0 1 8
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

example g292 0 1 81
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

pwn evolution
PWN Evolution

see Gelfand et al. 2009

energy input and swept-up

ejecta mass

PWN evolution

Patrick Slane MODE SNR/PWN Workshop

pwn evolution1
PWN Evolution

energy input and swept-up

ejecta mass

Vorster et al. 2013

PWN evolution

Patrick Slane MODE SNR/PWN Workshop

evolution of pwn emission
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

evolution of pwn emission1
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

evolution of pwn emission2
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

injection from relativistic shocks
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

pwn structure evolution 3c 58
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

pwn structure evolution snr 0540 69
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

g21 5 0 9
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

g21 5 0 91
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

g21 5 0 92
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

rs interactions g327 1 1 1
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

rs interactions g327 1 1 11
pringsRS Interactions: G327.1-1.1

prongs

cometary

structure

tail

pulsar + torus?

Patrick Slane MODE SNR/PWN Workshop

Temim et al. 2009

rs interactions g327 1 1 12
RS Interactions: G327.1-1.1

prongs

cometary

structure

tail

pulsar + torus?

Radio

Simulation

Patrick Slane MODE SNR/PWN Workshop

Temim et al. 2009

rs interactions msh 15 56
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

rs interactions msh 15 561
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

rs interactions msh 15 562
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

vela x an evolved pwn
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

slide29
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

slide30
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

take away
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

summary
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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