The pulsar wind nebula associated with PSR J1826 - 1334 , HESS J1825 - 137 , is a bright very high energy source with an angular extent of \sim 1 ^ { \circ } and spatially-resolved spectroscopic TeV measurements .
The gamma-ray spectral index is observed to soften with increasing distance from the pulsar , likely the result of cooling losses as electrons traverse the nebula .
We describe analysis of X-ray data of the extended nebula , as well as 3-D time-dependent spectral energy distribution modeling , with emphasis on the spatial variations within HESS J1825 - 137 .
The multi-wavelength data places significant constraints on electron injection , transport , and cooling within the nebula .
The large size and high nebular energy budget imply a relatively rapid initial pulsar spin period of 13 \pm 7 ms and an age of 40 \pm 9 kyr .
The relative fluxes of each VHE zone can be explained by advective particle transport with a radially decreasing velocity profile with v ( r ) \propto r ^ { -0.5 } .
The evolution of the cooling break requires an evolving magnetic field which also decreases radially from the pulsar , B ( r,t ) \propto r ^ { -0.7 } \dot { E } ( t ) ^ { 1 / 2 } .
Detection of 10 TeV flux \sim 80 pc from the pulsar requires rapid diffusion of high energy particles with \tau _ { esc } \approx 90 ( R / 10 pc ) ^ { 2 } ( E _ { e } / 100 TeV ) ^ { -1 } year , contrary to the common assumption of toroidal magnetic fields with strong magnetic confinement .
The model predicts a rather uniform Fermi LAT surface brightness out to \sim 1 ^ { \circ } from the pulsar , in good agreement with the recently discovered LAT source centered 0.5 ^ { \circ } southwest of PSR J1826 - 1334 with extension 0.6 \pm 0.1 ^ { \circ } .