We present an analysis of gamma-ray data obtained with the Large Area Telescope ( LAT ) onboard the Fermi Gamma-ray Space Telescope in the region around SNR S147 ( G180.0 - 1.7 ) .
A spatially extended gamma-ray source detected in an energy range of 0.2–10 GeV is found to coincide with SNR S147 .
We confirm its spatial extension at > 5 \sigma confidence level .
The gamma-ray flux is ( 3.8 \pm 0.6 ) \times 10 ^ { -8 } photons cm ^ { -2 } s ^ { -1 } , corresponding to a luminosity of 1.3 \times 10 ^ { 34 } ( d / 1.3 kpc ) ^ { 2 } erg s ^ { -1 } in this energy range .
The gamma-ray emission exhibits a possible spatial correlation with prominent H \alpha filaments of S147 .
There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538 + 2817 .
The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral \pi mesons produced through the proton–proton collisions in the filaments .
Reacceleration of pre-existing CRs and subsequent adiabatic compression in the filaments is sufficient to provide the required energy density of high-energy protons .