We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the direction of the inner 10 • around the Galactic Center with the intention of constraining, or finding evidence of, annihilating dark matter. We find that the morphology and spectrum of the emission between 1.25 • and 10 • from the Galactic Center is well described by a the processes of decaying pions produced in cosmic ray collisions with gas, and the inverse Compton scattering of cosmic ray electrons in both the disk and bulge of the Inner Galaxy, along with gamma rays from known points sources in the region. The observed spectrum and morphology of the emission within approximately 1.25 • (∼ 175 parsecs) of the Galactic Center, in contrast, departs from the expectations for by these processes. Instead, we find an additional component of gamma ray emission that is highly concentrated around the Galactic Center. The observed morphology of this component is consistent with that predicted from annihilating dark matter with a cusped (and possibly adiabatically contracted) halo distribution (ρ ∝ r −γ , with γ = 1.18 to 1.33). The observed spectrum of this component, which peaks at energies between 1-4 GeV (in E 2 units), can be well fit by a 7-10 GeV dark matter particle annihilating primarily to tau leptons with a cross section in the range of σv = 4.6 × 10 −27 to 5.3 × 10 −26 cm 3 /s, depending on how the dark matter distribution is normalized. We also discuss other sources for this emission, including the possibility that much of it originates from the Milky Way's supermassive black hole.PACS numbers: 95.35.+d; 95.85.Pw

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Multiple lines of evidence indicate an anomalous injection of high-energy e + e − in the Galactic halo. The recent e + fraction spectrum from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) shows a sharp rise up to 100 GeV. The Fermi Gamma-ray Space Telescope has found a significant hardening of the e + e − cosmic ray spectrum above 100 GeV, with a break, confirmed by HESS at around 1 TeV. The Advanced Thin Ionization Calorimeter (ATIC) has also detected detected a similar excess, falling back to the expected spectrum at 1 TeV and above. Excess microwaves towards the galactic center in the WMAP data are consistent with hard synchrotron radiation from a population of 10-100 GeV e + e − (the WMAP "Haze"). We argue that dark matter annihilations can provide a consistent explanation of all of these data, focusing on dominantly leptonic modes, either directly or through a new light boson. Normalizing the signal to the highest energy evidence (Fermi and HESS), we find that similar cross sections provide good fits to PAMELA and the Haze, and that both the required cross section and annihilation modes are achievable in models with Sommerfeld-enhanced annihilation. These models naturally predict significant production of gamma rays in the galactic center via a variety of mechanisms.Most notably, there is a robust inverse-Compton scattered (ICS) gamma-ray signal arising from the energetic electrons and positrons, detectable at Fermi/GLAST energies, which should provide smoking gun evidence for this production.

Recent preliminary results from the PAMELA experiment indicate the presence of an excess of cosmic ray positrons above 10 GeV. In this letter, we consider possibility that this signal is the result of dark matter annihilations taking place in the halo of the Milky Way. Rather than focusing on a specific particle physics model, we take a phenomenological approach and consider a variety of masses and two-body annihilation modes, including W + W − , Z 0 Z 0 , bb, τ + τ − , µ + µ − , and e + e − . We also consider a range of diffusion parameters consistent with current cosmic ray data. We find that a significant upturn in the positron fraction above 10 GeV is compatible with a wide range of dark matter annihilation modes, although very large annihilation cross sections and/or boost factors arising from inhomogeneities in the local dark matter distribution are required to produce the observed intensity of the signal. We comment on constraints from gamma rays, synchrotron emission, and cosmic ray antiproton measurements. PACS numbers: 95.35.+d; 98.70.Sa; 96.50.S; 95.55.Vj