COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Pulsar Wind Nebulae Observations of COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Jet/Torus Structure in PWNe Lyubarsky 2002 Anisotropic flux with maximum energy flux in equatorial zone - radial particle outflow - striped wind from Poynting flux decreases away from equator Wind termination shock is farther from pulsar at equator than along axis Magnetization is low in equatorial region due to dissipation in striped wind (reconnection?) - no collimation along equator; an equatorial disk (i.e. torus) forms 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 Patrick Slane (CfA) Pulsar Wind Nebulae Expansion boundary condition at forces wind termination shock at - wind goes from v = c/3 1/2 inside R w to v ~ R N /t at outer boundary Pulsar accelerates particle wind - wind inflates bubble of particles and magnetic flux - particle flow in B-field creates synchrotron nebula Blast Wave H or ejecta shell - spectral break at where synchrotron lifetime of particles equals SNR age - radial spectral variation from burn-off of high energy particles Pulsar wind is confined by pressure in nebula - wind termination shock Slane et al b Pulsar Wind MHD Shock Particle Flow logarithmic radial scale } R F COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Broadband Emission from PWNe Spin-down power is injected into the PWN at a time-dependent rate 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 & dE Jager 2006) Zhang et al. 2008 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Broadband Emission from PWNe Del Zanna et al Volpi et al 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 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Connecting the Synchrotron and IC Emission Energetic electrons in PWNe produce both synchrotron and inverse-Compton emission - for electrons with energy E TeV, 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) = S give B : For low B, synchrotron lifetime is long, and f ic /f s is large - can expect bright TeV emission from collection of long-lived electrons COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) A Point About Injection: 3C 58 Slane et al 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 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) A Point About Injection: 3C 58 3C 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 E Flux Density Injection Nebula Synchrotron Break COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Spitzer Observations of 3C 58 VLA IRAC 3.6 m Chandra Bietenholz 2006 IRAC 4.5 m Slane et al. 2004Slane et al 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 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Spitzer Observations of 3C 58 3C 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 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; TeV observations should provide constraints Slane et al. 2008 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Spitzer Observations of 3C 58 PRELIMINARY 3C 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 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; TeV observations should provide constraints COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Kes 75 Bright wind nebula powered by PSR J ( Edot = ) - 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 Ng et al. 2008 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Kes 75 See also poster E11.62: (S. Safi-Harb et al.) 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 (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) Ng et al Djannati-Atai et al. 2008 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) HESS J arcmin Lemiere et al Extended source identified in HESS GPS - no known pulsar associated with source - may be associated with SNR G 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 - L x ~ erg s -1 Edot ~ erg s -1 - X-ray and TeV spectrum well-described by leptonic model with B ~ 6 G and t ~ 15 kyr COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) PWNe and Their SNRs ISM Shocked ISM Shocked EjectaUnshocked Ejecta PWN Pulsar Wind Forward Shock Reverse Shock PWN Shock Pulsar Termination Shock Pulsar Wind - sweeps up ejecta; shock decelerates flow, accelerates particles; PWN forms Supernova Remnant - 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 Gaensler & Slane 2006 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) 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 Vela X van der Swaluw, Downes, & Keegan 2003 t = 10,000 yrt = 20,000 yrt = 30,000 yrt = 56,000 yr Blondin et al RS interaction displaces PWN, produces turbulent structures, and mixes in ejecta COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Vela X LaMassa et al 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 10x 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 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) Vela X de Jager et al 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 COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) G : Another Reverse-Shock Interaction Temim et al G 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 - L x suggests Edot ~ 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 E11.57: Chandra and XMM Observations of the Composite SNR G (Tea Temim et al.) COSPAR 2008, Montreal, 18 July Patrick Slane (CfA) 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 TeV sources offset from pulsars - multiwavelength observations needed to secure this scenario (e.g. Vela X. HESS J , and others) Low-field, old PWNe may fade from X-ray view, but still be detectable sources of TeV emission - VHE -ray surveys are likely to continue uncovering new members of this class