X-ray Studies of Unidentified Galactic TeV Gamma-ray Sources

Abstract

Many of the recently discovered Galactic TeV sources remain unidentified to date. A large fraction of the sources is possibly associated with relic pulsar wind nebula (PWN) systems. One key question here is the maximum energy (beyond TeV) attained in the compact PWNe. Hard X‐ray emission can trace those particles, but current non‐focussing X‐ray instruments above 10 keV have difficulties to deconvolve the hard pulsar spectrum from its surrounding nebula.Some of the new TeV sources are also expected to originate from middle‐aged and possibly even from old supernova remnants (SNR). But no compelling case for such an identification has been found yet. In established young TeV‐emitting SNRs, X‐ray imaging above 10 keV could help to disentangle the leptonic from the hadronic emission component in the TeV shells, if secondary electrons produced in hadronic collisions can be effectively detected. As SNRs get older, the high energy electron component is expected to fade away. This may allow to verify the picture through X‐ray spectral evolution of the source population.Starting from the lessons we have learned so far from X‐ray follow‐up observations of unidentified TeV sources, prospects for Simbol‐X to resolve open questions in this field will be discussed.