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Simulations Revive Dark-Matter Case for Milky Way’s Gamma-Ray Excess

The result shifts the focus to energy spectra that upcoming CTA observations could use to tell dark matter from millisecond pulsars.

Overview

  • A team led by the Leibniz Institute for Astrophysics Potsdam, with collaborators at the Hebrew University of Jerusalem and Johns Hopkins University, reports in Physical Review Letters that high-resolution Hestia simulations produce a clumpy, boxy dark-matter distribution near the Galactic center.
  • The modeled morphology matches the Fermi-detected excess’s flattened shape, removing a longstanding shape-based objection and placing dark-matter annihilation and millisecond pulsars on comparable footing.
  • In the simulations, merger-driven dynamics yield a non-spherical dark-matter profile arranged similarly to the central stellar distribution, which can reproduce the observed excess if annihilation occurs.
  • Observational clues remain mixed, with a similar gamma-ray glow in a dwarf galaxy favoring annihilation while LHAASO’s non-detection in the Galactic center tightens constraints on viable WIMP masses and energies.
  • Discriminating between the hypotheses now hinges on spectral signatures, where a sharp high-energy cutoff would point to dark matter and a more extended spectrum would support pulsars, measurements expected to be enabled by the Cherenkov Telescope Array in Chile and Spain.