Fermi Gamma-ray Space Telescope

Search for Cosmic Ray Electron Anisotropies with the Fermi-LAT Pass 8 data

M. N. Mazziotta
F. Costanzo, F. Loparco, N. Di Lalla, on behalf of the Fermi-LAT Collaboration

Abstract:

The Fermi Large Area Telescope (LAT) has collected a huge sample of high-energy galactic cosmic-ray electrons/positrons (CREs) since the beginning of its operation. Possible anisotropies in the arrival directions of CREs could be a signature of the presence of nearby sources. The LAT collaboration has moved to the new Pass 8 event reconstruction to fully exploit the instrument performance. The present data sample will allow us to probe dipole anisotropies at a level of 10-3. At this level of sensitivity all features that could mimic true anisotropies should be accounted for, as for instance the effects of the geomagnetic field. In fact, the Fermi satellite, during its first 7 years of operation, scanned the full sky with several different attitudes and this might affect the observed arrival directions of CREs in the large field of view of the LAT. We present a detailed study to optimize the selection of the CRE events to be used for anisotropy searches. We also present the prospects of this measurement and some preliminary results.