Abstract
Cosmic-ray electrons provide a probe of the origin and propagation mechanisms of cosmic rays in local galactic environmentThe Large Area Telescope (LAT), on board the Fermi mission, is a pair-conversion space telescope for high-energy electromagnetic radiation, operating in low Earth orbit since June 2008. The LAT has collected the largest high-energy cosmic-ray electron sample to date, with more than 10k events above 1 TeV. The event selection and reconstruction capability exploits the performance of the recently improved event-level analysis developed by the Fermi-LAT Collaboration.We present a new measurement of the inclusive spectrum of cosmic-ray electrons and positrons performed on seven years of data, in an energy range from 7 GeV up to 2 TeV.
Highlights
While propagating throughout the Galaxy, high-energy electrons and positron (CRE) rapidly lose energy by inverse Compton scattering on the interstellar radiation field and by synchrotron emission on the Galactic magnetic field
Since all these processes can affect the CRE spectrum after its injection by the sources, the observed spectrum is sensitive to the environment, determining how CRE propagate through the Galaxy
The Large Area Telescope (LAT) is a 4×4 array of identical towers, each made by a tracker-converter (TRK) and a calorimeter module (CAL)
Summary
While propagating throughout the Galaxy, high-energy electrons and positron (CRE) rapidly lose energy by inverse Compton scattering on the interstellar radiation field and by synchrotron emission on the Galactic magnetic field. The shape of the CRE spectrum from about 100 GeV up to few TeV can provide evidence of the presence of local CRE sources. These can be of astrophysical, like Supernova Remnants (SNR) or Pulsar Wind Nebulae (PWN), or of exotic nature, as the elusive dark matter. Lower-energy CRE are affected by energy-dependent diffusive losses, convection in the interstellar medium, and perhaps reacceleration by second-order Fermi processes during transport from their sources. Since all these processes can affect the CRE spectrum after its injection by the sources, the observed spectrum is sensitive to the environment, determining how CRE propagate through the Galaxy. These results can be jointly interpreted with the presence of local CRE sources with a spectral cutoff at about this energy
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