2008ApJ...689L.125D

Morphologically, it appears as if the Vela X pulsar wind nebula (PWN) consists of two emission regions: whereas X-ray (∼1 keV) and very high energy (VHE) H.E.S.S. γ-ray observations appear to define a cocoon-type shape south of the pulsar, radio observations reveal an extended area of size 2°x3° (including the cocoon area), also south of the Vela pulsar. Since no wide field of view (FoV) observations of the synchrotron emission between radio and X-rays are available, we do not know how the lepton (e^±) spectra of these two components connect or how the morphology changes with energy. Currently, we find that two distinct lepton spectra describe the respective radio and X-ray/VHE γ-ray spectra, with a field strength of 5 µG self-consistently describing a radiation spectral break (or energy maximum) in the multi-TeV domain as observed by H.E.S.S. (if interpreted as IC radiation), while predicting the total hard X-ray flux above 20 keV (measured by the wide FoV INTEGRAL instrument) within a factor of 2. If this same field strength is also representative of the radio structure (including filaments), the implied IC component corresponding to the highest radio frequencies should reveal a relatively bright high-energy γ-ray structure, and Fermi LAT should be able to resolve it. A higher field strength in the filaments would, however, imply fewer leptons in Vela X and hence a fainter Fermi LAT signal.