On The Origin Of The Gamma Rays From The Galactic Center (1110.0006v1)

Abstract: The region surrounding the center of the Milky Way is both astrophysically rich and complex, and is predicted to contain very high densities of dark matter. Utilizing three years of data from the Fermi Gamma Ray Space Telescope (and the recently available Pass 7 ultraclean event class), we study the morphology and spectrum of the gamma ray emission from this region and find evidence of a spatially extended component which peaks at energies between 300 MeV and 10 GeV. We compare our results to those reported by other groups and find good agreement. The extended emission could potentially originate from either the annihilations of dark matter particles in the inner galaxy, or from the collisions of high energy protons that are accelerated by the Milky Way's supermassive black hole with gas. If interpreted as dark matter annihilation products, the emission spectrum favors dark matter particles with a mass in the range of 7-12 GeV (if annihilating dominantly to leptons) or 25-45 GeV (if annihilating dominantly to hadronic final states). The intensity of the emission corresponds to a dark matter annihilation cross section consistent with that required to generate the observed cosmological abundance in the early universe (sigma v ~ 3 x 10^-26 cm^3/s). We also present conservative limits on the dark matter annihilation cross section which are at least as stringent as those derived from other observations.

• The paper identifies a spatially extended gamma ray component peaking between 300 MeV and 10 GeV, challenging single-source emission models.
• The paper’s analysis shows that gamma rays may derive from dark matter annihilations with optimal particle masses of 7–12 GeV or 25–45 GeV, consistent with thermal relic predictions.
• The paper employs three years of Fermi data with gamma ray mapping and source subtraction techniques to reveal emission patterns potentially linked to cosmic ray interactions near the black hole.

Analysis of Gamma Ray Emission from the Galactic Center: A Study on Potential Origins

This paper, authored by Dan Hooper and Tim Linden, explores the gamma ray emission from the Galactic Center using data from the Fermi Gamma Ray Space Telescope. The paper investigates the morphological and spectral characteristics of gamma radiation in this region, hypothesizing potential origins, including dark matter annihilation and cosmic ray interactions.

The authors identify a spatially extended component of gamma ray emission peaking between 300 MeV and 10 GeV from their analysis. This extended component is consistent across various studies, supporting its credibility. The central aim is to determine whether the observed gamma ray emission can be attributed to dark matter annihilations or other astrophysical phenomena like interactions involving the Milky Way's supermassive black hole.

Key Findings

1. Emission Characteristics: The spatially extended gamma rays exhibit a consistent spectrum, distinct from a single point source. This aspect challenges models positing direct emissions from the central black hole but aligns with theories involving diffusing cosmic rays or dark matter annihilations.
2. Dark Matter Hypothesis: If the gamma ray emissions are products of dark matter annihilations, the optimal mass for these particles would be 7-12 GeV (for annihilations to leptons) or 25-45 GeV (for hadronic final states). The annihilation cross section aligns with the value predicted for thermal relics, suggesting a viable explanation using dark matter cosmologies.
3. Proton Acceleration Scenario: The scenario where protons, accelerated by the central black hole, produce gamma rays via interactions with gas, presents a compelling alternative. However, this faces challenges in explaining the rapid gamma ray flux increase observed within specific energy ranges.

Analytical Methodology

The analysis relies on data from three years of observations, which are used to generate gamma ray maps, subtract known astrophysical sources, and produce a template for diffuse emissions associated with cosmic ray processes. By examining these maps, the researchers establish that a considerable portion of the emission is non-point-like and possibly related to dark matter or ancillary astrophysical sources.

Implications and Future Considerations

The paper's results contribute significantly to understanding the potential gamma ray signatures of dark matter annihilations, proposing that a concentrated dark matter density profile consistent with adiabatic contraction could account for the observed emissions. The constraints on the annihilation cross-section derived here are competitive with those from other observations, including those from dwarf spheroidal galaxies.

The findings suggest future research directions, including more precise modeling of galactic center dynamics and improved observational constraints on electron and proton spectra from suspected sources. Further refinement of dark matter models and the paper of synchrotron emissions could elucidate the nature of these observations.

In summary, Hooper and Linden’s research presents a meticulous analysis of gamma ray emissions, indicating potential intersections between dark matter physics and astrophysical processes at the Galactic Center. The paper lays essential groundwork for future investigations into the complex interplay of cosmic phenomena in this densely populated and energetic galactic region.