Observations of Pulsar Wind Nebulae Patrick Slane Cf

Observations of Pulsar Wind Nebulae Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

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 • Magnetization is low in equatorial region due to dissipation in striped wind (reconnection? ) - no collimation along equator; an equatorial disk (i. e. torus) forms • Wind termination shock is farther from pulsar at equator than along axis Lyubarsky 2002 Patrick Slane (Cf. A) • At higher latitudes, average B field is a maximum - this can turn the flow inward at high latitudes, collimating flow and forming a jet beyond TS, where flow is mildly (or non-) relativistic COSPAR 2008, Montreal, 18 July

Pulsar Wind Nebulae } • Expansion boundary condition at forces wind termination shock at logarithmic radial scale G Pulsar b Wind MH k D Shoc F Particle Flow + ++ - wind goes from v = c/31/2 inside Rw to v ~ RN/t at outer boundary + + • Pulsar wind is confined by pressure in nebula R - wind termination shock Blast Wave Ha or ejecta shell • Pulsar accelerates - spectral break at particle wind - wind inflates bubble where synchrotron of particles and lifetime of particles magnetic flux equals SNR age - particle flow in B-field - radial spectral variation creates synchrotron from burn-off of high Patrick Slane (Cf. A) nebula energy particles Slane et al. 2004 COSPAR 2008, Montreal, 18 July

Broadband Emission from PWNe • Spin-down power is injected into the PWN at a time-dependent rate Zhang et al. 2008 • Based on studies of Crab Nebula, there appear to be two populations – relic radio-emitting electrons and electrons injected in wind (Atoyan & Aharonian 1996) • Get associated synchrotron and IC emission from electron population, and some assumed B field (e. g. Venter & d. E Jager 2006) Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Broadband Emission from PWNe Del Zanna et al. 2006 • More realistically, assume wind injected at termination shock, with radial particle distribution and latitude-dependent magnetic component: • Evolve nebula considering radiative and adiabatic losses to obtain time- and spatially-dependent electron spectrum and B field (e. g. Volpi et al. 2008) - integrate over synchrotron and IC emissivity to get spectrum Volpi et al. 2008 Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Connecting the Synchrotron and IC Emission • Energetic electrons in PWNe produce both synchrotron and inverse-Compton emission - for electrons with energy ETe. V, synchrotron inverse-Compton - comparing photon energies from given electron population gives B (e. g. Atoyan & Aharonian 1999) • Similarly, relative fluxes f. E = E 2 f(E) = n. Sn give B: • For low B, synchrotron lifetime is long, and fic/fs is large - can expect bright Te. V emission from collection of long-lived electrons Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

A Point About Injection: 3 C 58 • 3 C 58 is a bright, young PWN - morphology similar to radio/x-ray; suggests low magnetic field - low-frequency spectral break suggests possible injection break Slane et al. 2004 • PWN and torus region observed in Spitzer/IRAC and CFHT observations - jet structure not seen above diffuse emission Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

A Point About Injection: 3 C 58 • 3 C 58 is a bright, young PWN Flux Density Nebula Synchrotron Break - morphology similar to radio/x-ray; suggests low magnetic field - low-frequency spectral break suggests possible injection break • PWN and torus region observed in Spitzer/IRAC and CFHT observations - jet structure not seen above diffuse emission Injection E Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Spitzer Observations of 3 C 58 VLA IRAC 4. 5 m • 3 C 58 is a bright, young PWN - morphology similar to radio/x-ray; suggests low magnetic field - low-frequency spectral break suggests possible injection break • PWN and torus region observed in Spitzer/IRAC and CFHT observations - jet structure not seen above diffuse emission Bietenholz 2006 Chandra Slane et al. 2004 Patrick Slane (Cf. A) IRAC 3. 6 m Slane et al. 2008 COSPAR 2008, Montreal, 18 July

Spitzer Observations of 3 C 58 • 3 C 58 is a bright, young PWN Slane et al. 2008 - morphology similar to radio/x-ray; suggests low magnetic field - low-frequency spectral break suggests possible injection break • PWN and torus region observed in Spitzer/IRAC and CFHT observations - jet structure not seen above diffuse emission • IR flux for entire nebula falls within extrapolation of x-ray spectrum - indicates single break just below IR - sub-mm observations would be of interest Slane et al. 2008 Patrick Slane (Cf. A) • Torus spectrum requires change in slope between IR and x-ray bands - challenges assumptions of single power law for injection into nebula; Te. V observations should provide constraints COSPAR 2008, Montreal, 18 July

Spitzer Observations of 3 C 58 • 3 C 58 is a bright, young PWN PRELIMINARY - morphology similar to radio/x-ray; suggests low magnetic field - low-frequency spectral break suggests possible injection break • PWN and torus region observed in Spitzer/IRAC and CFHT observations - jet structure not seen above diffuse emission • IR flux for entire nebula falls within extrapolation of x-ray spectrum - indicates single break just below IR - sub-mm observations would be of interest • Torus spectrum requires change in slope between IR and x-ray bands - challenges assumptions of single power law for injection into nebula; Te. V observations should provide constraints Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Ng et al. 2008 Kes 75 • Bright wind nebula powered by PSR J 1846 -0258 (Edot = 1036. 9) - jet-like structure defines rotation axis (Helfand et al. 2003) • Deep Chandra observation reveals moving clumps, arc-like structure, Crab-like bays, inner/outer jet features, and abrupt jet termination in south (Ng et al. 2008) - best-fit structure to ordered structure yields jet/torus with clump in north - jet spectrum is harder than surrounding regions, suggesting high-velocity flow Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Ng et al. 2008 Kes 75 • Spectral index shows general steepening with radius in diffuse nebula • HESS observations reveal VHE -ray emission - Lx/L B ~ 15 G , consistent w/ large X-ray size • RXTE observations reveal magnetar-like bursts from PSR J 1846 -0258 (Gavril et al. 2008) - Chandra observation reveal brightening of pulsar as well - also see brightening of northern clump and inner jet (though unrelated to bursts given flow timescales) Patrick Djannati-Atai et Slane al. 2008(Cf. A) See also poster E 11. 62: (S. Safi-Harb et al. ) COSPAR 2008, Montreal, 18 July

Lemiere et al. 2008 HESS J 1640 -465 5 arcmin • Extended source identified in HESS GPS - no known pulsar associated with source - may be associated with SNR G 338. 3 -0. 0 • XMM observations (Funk et al. 2007) identify extended X-ray emission, securing an associated X-ray PWN • Chandra observations (Lemiere et al. 2008) reveal point source within extended nebula, apparently identifying associated neutron star - HI absorption indicates a distance d ~ 8 – 13 kpc - Lx ~ 1033. 1 erg s-1 Edot ~ 1036. 7 erg s-1 - X-ray and Te. V spectrum well-described by leptonic model with B ~ 6 G and t ~ 15 kyr Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

PWNe and Their SNRs Shocked Ejecta Shocked ISM � ISM Unshocked Ejecta Pulsar Termination Shock PWN Pulsar Wind PWN Shock Reverse Shock Forward Shock • Pulsar Wind - sweeps up ejecta; shock decelerates flow, accelerates particles; PWN forms • Supernova Remnant Gaensler & Slane 2006 - sweeps up ISM; reverse shock heats ejecta; ultimately compresses PWN; particles accelerated at forward shock generate magnetic turbulence; other particles scatter off this and receive additional acceleration Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Vela X RS interaction displaces PWN, produces turbulent structures, and mixes in ejecta t = 10, 000 yr t = 20, 000 yr t = 30, 000 yr t = 56, 000 yr Blondin et al. 2001 van der Swaluw, Downes, & Keegan 2003 • Vela X is the PWN produced by the Vela pulsar - located primarily south of pulsar - apparently the result of relic PWN being disturbed by asymmetric passage of the SNR reverse shock (e. g. Blondin et al. 2001) • Elongated “cocoon-like” hard X-ray structure extends southward of pulsar - clearly identified by HESS as an extended VHE structure - this is not the pulsar jet (which is known to be directed to NW); presumably the result of reverse shock interaction Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Vela X La. Massa et al. 2008 • XMM spectrum shows nonthermal and ejecta-rich thermal emission from end of cocoon - reverse-shock crushed PWN and mixed-in ejecta? • Radio, X-ray, and -ray measurements appear consistent with synchrotron and I-C emission from power law particle spectrum w/ two spectral breaks - density derived from thermal emission 10 x lower than needed for pion-production to provide observed -ray flux - much larger X-ray coverage of Vela X is required to fully understand structure Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Vela X de Jager et al. 2008 • Radio and VHE spectrum for entire PWN suggests presence of two distinct electron populations - radio-emitting particles may be relic population; higher energy electrons injected by pulsar • Maximum energy of radio-emitting electrons not well-constrained - this population will generate IC emission in GLAST band; spectral features will identify indentify emission from distinct up-scattered photon populations - upcoming observations will provide strong constraints on this electron population Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

G 327. 1 -1. 1: Another Reverse-Shock Interaction Temim et al. 2008 • G 327. 1 -1. 1 is a composite SNR with a bright central nebula - nebula is offset from SNR center - “finger” of emission extends toward northwest • X-ray observations reveal compact source at tip of radio finger - trail of emission extends into nebula - Lx suggests Edot ~ 1037. 3 erg s-1 • Compact X-ray emission is extended; presumably pulsar torus - PWN has apparently been disturbed by SNR reverse shock, and is now re-forming around pulsar, much like Vela X et al. • Curious prong-like structures extend in direction opposite the relic PWN - these prongs appear to connect to a bubble blown by the pulsar in the SNR interior, apparently in the region recently crossed by the reverse shock See poster E 11. 57: Chandra and XMM Observations of the Composite SNR G 327. 1 -1. 1 (Tea Temim et al. ) Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July

Conclusions • PWNe are reservoirs of energetic particles injected from pulsar - morphology of nebulae reveals underlying geometry - synchrotron and inverse-Compton emission places strong constraints on the underlying particle spectrum and magnetic field • Modeling of broadband emission constrains evolution of particles and B field - modeling form of injection spectrum and full evolution of particles still in its infancy • Reverse-shock interactions between SNR and PWNe distort nebula and may explain Te. V sources offset from pulsars - multiwavelength observations needed to secure this scenario (e. g. Vela X. HESS J 1825 -137, and others) • Low-field, old PWNe may fade from X-ray view, but still be detectable sources of Te. V emission - VHE -ray surveys are likely to continue uncovering new members of this class Patrick Slane (Cf. A) COSPAR 2008, Montreal, 18 July