Dark matter electron anisotropy: a universal upper limit

Abstract

We study the dipole anisotropy in the arrival directions of high energy CR electrons and positrons (CRE) of Dark Matter (DM) origin. We show that this quantity is very weakly model dependent and offers a viable criterion to discriminate among CRE from DM or from local discrete sources, like e.g. pulsars. In particular, we find that the maximum anisotropy which DM can provide is to a very good approximation a universal quantity and, as a consequence, if a larger anisotropy is detected, this would constitute a strong evidence for the presence of astrophysical local discrete CRE sources, whose anisotropy, instead, can be naturally larger than the DM upper limit. We further find that the main source of anisotropy from DM is given by the fluctuation in the number density of DM sub-structures in the vicinity of the observer and we thus devote special attention to the study of the variance in the sub-structures realization implementing a dedicated Montecarlo simulation. Such scenarios will be probed in the next years by Fermi-LAT, providing new hints, or constraints, about the nature of DM.

23 pages, 7 figures

References in corpus (30)

• Observation of an anomalous positron abundance in the cosmic radiation
• A Theory of Dark Matter
• Measurement of the Cosmic Ray e+ plus e- spectrum from 20 GeV to 1 TeV with the Fermi Large Area Telescope
• Measurement of separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope
• A common mass scale for satellite galaxies of the Milky Way
• CMB Constraints on WIMP Annihilation: Energy Absorption During the Recombination Epoch
• Fermi LAT observations of cosmic-ray electrons from 7 GeV to 1 TeV
• The origin of the positron excess in cosmic rays
• On possible interpretations of the high energy electron-positron spectrum measured by the Fermi Large Area Telescope
• Discovery of Localized Regions of Excess 10-TeV Cosmic Rays
• Updated CMB constraints on Dark Matter annihilation cross-sections
• Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. II: anisotropy
• The Large Scale Cosmic-Ray Anisotropy as Observed with Milagro
• Dark matter interpretation of recent electron and positron data
• Observation of an Anisotropy in the Galactic Cosmic Ray arrival direction at 400 TeV with IceCube
• Measurement of the Anisotropy of Cosmic Ray Arrival Directions with IceCube
• Astrophysical models for the origin of the positron "excess"
• Local Magnetic Turbulence and TeV-PeV Cosmic Ray Anisotropies
• Searches for Cosmic-Ray Electron Anisotropies with the Fermi Large Area Telescope
• Magnetic reconnection as the cause of cosmic ray excess from the heliospheric tail
• The puzzling MILAGRO hot spots
• Implications of the Cosmic Ray Electron Spectrum and Anisotropy measured with Fermi-LAT
• Probing Nearby CR Accelerators and ISM Turbulence with Milagro Hot Spots
• The Milagro anticenter hot spots: cosmic rays from the Geminga supernova ?
• Cosmic ray electrons and positrons from discrete stochastic sources
• Discriminating the source of high-energy positrons with AMS-02
• Positrons from pulsar winds
• Constraints on Enhanced Dark Matter Annihilation from IceCube Results
• The contribution to the antimatter flux from individual dark matter substructures
• Observation of the anisotropy in arrival direction of Cosmic Rays with IceCube

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• The origin of Galactic cosmic rays: challenges to the standard paradigm
• Indirect and direct search for dark matter
• Origin of Small-Scale Anisotropies in Galactic Cosmic Rays
• Solution to the cosmic ray anisotropy problem
• Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data
• Dynamical Dark Matter and the Positron Excess in Light of AMS
• Extracting the size of the cosmic electron-positron anomaly
• Search for Features in the Cosmic-Ray Electron and Positron spectrum measured by the Fermi Large Area Telescope
• Observing small-scale $\gamma$-ray anisotropies with the Cherenkov Telescope Array
• An observable electron-positron anisotropy cannot be generated by dark matter
• Indirect searches for dark matter with the Fermi LAT instrument