Fermi Large Area Telescope Detection of the Young Supernova Remnant Tycho

After almost three years of data taking in sky-survey mode, the Fermi Large Area Telescope has detected γ-ray emission toward Tycho's supernova remnant (SNR). The Tycho SNR is among the youngest remnants in the Galaxy, originating from a Type Ia Supernova in AD 1572. The γ-ray integral flux from 400 MeV up to 100 GeV has been measured to be (3.5 ± 1.1stat ± 0.7syst)× 10–9 cm–2 s–1 with a photon index of 2.3 ± 0.2stat ± 0.1syst. A simple model consistent with TeV, X-ray, and radio data is sufficient to explain the observed emission as originating from π0 decays as a result of cosmic-ray acceleration and interaction with the ambient medium.