Unveiling extended gamma-ray emission around HESS J1813-178

is a very-high-energy gamma -ray source spatially coincident with the young and energetic pulsar and thought to be associated with its pulsar wind nebula (PWN). Recently, evidence for extended high-energy emission in the vicinity of the pulsar has been revealed in the Fermi Large Area Telescope (LAT) data. This motivates revisiting the region, taking advantage of improved analysis methods and an extended dataset. Using data taken by the High Energy Stereoscopic System (H.E.S.S.) experiment and the we aim to describe the gamma -ray emission in the region with a consistent model, to provide insights into its origin. We performed a likelihood-based analysis on 32 hours of H.E.S.S. data and 12 years of data and we fitted a spectro-morphological model to the combined datasets. These results allowed us to develop a physical model for the origin of the observed gamma -ray emission in the region. In addition to the compact very-high-energy gamma -ray emission centred on the pulsar, we find a significant yet previously undetected component along the Galactic plane. With data, we confirm extended high-energy emission consistent with the position and elongation of the extended emission observed with These results establish a consistent description of the emission in the region from GeV energies to several tens of TeV. This study suggests that is associated with a gamma -ray PWN powered by A possible origin of the extended emission component is inverse Compton emission from electrons and positrons that have escaped the confines of the pulsar and form a halo around the PWN.