Implications of H.E.S.S. observations of pulsar wind nebulae

摘要

In this review paper on pulsar wind nebulae (PWN) we discuss the propertiesof such nebulae within the context of containment against cross-field diffusion(versus normal advection), the effect of reverse shocks on the evolution ofoffset ``Vela-like'' PWN, constraints on maximum particle energetics, magneticfield strength estimates based on spectral and spatial properties, and theimplication of such field estimates on the composition of the wind. Asignificant part of the discussion is based on the High Energy StereoscopicSystem ({\it H.E.S.S.} or {\it HESS}) detection of the two evolved pulsar windnebulae Vela X (cocoon) and HESS J1825-137. In the case of Vela X (cocoon) wealso review evidence of a hadronic versus a leptonic interpretation, showingthat a leptonic interpretation is favored for the {\it HESS} signal. Theconstraints discussed in this review paper sets a general framework for theinterpretation of a number of offset, filled-center nebulae seen by {\it HESS}.These sources are found along the galactic plane with galactic latitudes$|b|\sim 0$, where significant amounts of molecular gas is found. In theseregions, we find that the interstellar medium is inhomogeneous, which has aneffect on the morphology of supernova shock expansion. One consequence of thiseffect is the formation of offset pulsar wind nebulae as observed.