Distinguishing Between Dark Matter and Pulsar Origins of the ATIC Electron Spectrum With Atmospheric Cherenkov Telescopes

Abstract

Recent results from the Advanced Thin Ionization Calorimeter (ATIC) balloon experiment have identified the presence of a spectral feature between approximately 300 and 800 GeV in the cosmic ray electron spectrum. This spectral feature appears to imply the existence of a local (within about 1 kpc) source of high energy electrons. Emission from a local pulsar and dark matter annihilations have each been put forth as possible origins of this signal. In this letter, we consider the sensitivity of ground based atmospheric Cherenkov telescopes to electrons and show that observatories such as HESS and VERITAS should be able to resolve this feature with sufficient precision to discriminate between the dark matter and pulsar hypotheses with considerably greater than 5 sigma significance, even for conservative assumptions regarding their performance. In addition, this feature provides an opportunity to perform an absolute calibration of the energy scale of ground based, gamma ray telescopes.

Figures (2)

• Figure 1: The cosmic ray electron spectrum as measured by ATIC atic compared to the spectrum predicted from three possible sources: a nearby pulsar (red), annihilation of $800$ GeV dark matter annihilating to $W^+W^-$ (blue), and annihilation of $620$ GeV Kaluza-Klein dark matter (which annihilates to $e^+ e^-$, $\mu^+ \mu^-$, and $\tau^+ \tau^-$ 20% of the time each). In each case, the source spectrum was added to a background power-law spectrum with a spectral slope of -3.2 (dashed).
• Figure 2: The projected cosmic ray electron spectrum for an ACT such as HESS or VERITAS (including misidentified hadrons). Errors are statistical. The very large collecting area of ACTs allow for a much more detailed measurement than is possible from balloon or satellite experiments. With such a measurement the two scenarios shown above are clearly distinguishable.