Pulsar Wind Nebulae with H.E.S.S.: Establishing a Connection between high-power Pulsars and very-high-energy gamma-ray Sources

Abstract

Pulsars energise particles into lighthouse pencil beams and create extended relativistic outflows, pulsar wind nebulae (PWNe). In the very-high-energy (VHE) gamma-ray wave band, these PWNe represent to date the most populous class of Galactic sources. Nevertheless, the details of the energy conversion mechanisms in the vicinity of pulsars are not well understood, nor is it known which pulsars are able to drive PWNe and emit high-energy radiation. Due to its large field of view and unprecedented sensitivity, H.E.S.S. is the first instrument to allow for deep surveys of the Galactic plane in VHE gamma rays. This work presents the first ever systematic investigation of the connection of VHE gamma-ray sources and PWNe. Besides presenting two new candidate PWNe detected in this search, it is shown that pulsars with large spin-down energy flux are indeed with high probability associated with VHE gamma-ray sources, implying the existence of an efficient mechanism by which a large fraction of pulsar spin-down energy is converted into kinetic energy of particles. The results presented here make it very likely that future more sensitive VHE gamma-ray instruments will detect a rapidly increasing number of lower-luminosity PWNe.