Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data

Abstract

The Large Area Telescope on board the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass~8 reconstruction. The present data sample can probe dipole anisotropies down to a level of $10^{-3}$. We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. The present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.

8 pages; 3 figures; Published in Phys. Rev. Lett. 118, 091103; Contact authors: Francesco Costanza [email protected] and M. Nicola Mazziotta [email protected]; Supplemental Material also available on the Ancillary files

References in corpus (5)

• On possible interpretations of the high energy electron-positron spectrum measured by the Fermi Large Area Telescope
• The angular power spectrum of the diffuse gamma-ray emission as measured by the Fermi Large Area Telescope and constraints on its Dark Matter interpretation
• Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data
• Implications of the Cosmic Ray Electron Spectrum and Anisotropy measured with Fermi-LAT
• Angular Power Spectra with Finite Counts

Cited by in corpus (4)

• Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons
• Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data
• Dark matter indirect signals with long-lived mediators
• Explanations of the DAMPE high energy electron/positron spectrum in the dark matter annihilation and pulsar scenarios