2011ApJ...729...93K

One of the most essential but uncertain processes for producing cosmic rays (CRs) and their spectra is how accelerated particles escape into the interstellar space. We propose that the CR electron spectra at ≳TeV energies can provide a direct probe of the CR escape complementary to the CR nuclei and gamma rays. We calculate the electron spectra from a young pulsar embedded in a supernova remnant (SNR), like Vela, taking into account the energy-dependent CR escape. SNRs would accelerate and hence confine particles with energies up to 10^15.5 eV. Only energetic particles can escape first, while the lower energy particles are confined and released later. Then the observed electron spectrum should have a low-energy cutoff the position of which marks the age of the pulsar/SNR. The low-energy cutoff is observable in the ≳TeV energy window, where other contaminating sources are expected to be few due to the fast cooling of electrons. The spectrum looks similar to a dark matter annihilation line if the low-energy cutoff is close to the high-energy intrinsic or cooling break. Future experiments, such as the Calorimetric Electron Telescope and Cherenkov Telescope Array, are capable of directly detecting the CR escape features toward revealing the origin of CRs.