Gamma-ray and radio tests of the e+e- excess from DM annihilations

Abstract

PAMELA and ATIC recently reported an excess in e+e- cosmic rays. We show that if it is due to Dark Matter annihilations, the associated gamma-ray flux and the synchrotron emission produced by e+e- in the galactic magnetic field violate HESS and radio observations of the galactic center and HESS observations of dwarf Spheroidals, unless the DM density profile is significantly less steep than the benchmark NFW and Einasto profiles.

Figures (4)

• Figure 1: Shape of DM density (left) and magnetic field (right) profiles discussed in the text, as a function of the galactocentric coordinate $r$.
• Figure 2: HESS observations of the Galactic Center (left) and Galactic Ridge (right) compared with the annihilation signals from our two sample models a1) (left) and b) (right), assuming a NFW profile and an annihilation cross section of $\sigma v = 10^{-23}$ cm$^3$/sec, and with the sum of the annihilation signal and a possible astrophysical background flux.
• Figure 3: We compare the region favored by PAMELA (green bands) and ATIC (red regions within the bands) with the bounds from HESS observations of the Galatic Center HessGC (blue continuous line), Galactic Ridge HessRidge (blue dot-dashed), and SgrDwarf HessSgrDwarf (blue dashed) and of observations of the Galactic Center at radio-frequencies $\nu=408\,{\rm GHz}$ by Davies et al. Davies (red lines) and at $\nu \sim 10^{14}\,{\rm Hz}$ by VLT VLT (upper purple lines, when present, for equipartition and constant magnetic field). We considered DM annihilations into $e^+ e^-$ (left column), $\mu^+\mu^-$ (middle), $\tau^+\tau^-$ (right), unity boost and Sommerfeld factors and the NFW (upper row), Einasto (middle), isothermal (lower) MW DM density profiles and the NFW (upper), large core (middle and lower) Sgr dSph DM density profiles.
• Figure 4: As in the previous fig. \ref{['fig:boundsNFW']}, but for the cases of DM annihilations into $W^+ W^-$ (left), $b\bar{b}$ (middle), $t\bar{t}$ (right).