Glow in the Dark Matter: Observing Galactic Halos with Scattered Light

Jonathan H. Davis (1) , Joseph Silk (1)

1 IAP - Institut d'Astrophysique de Paris

We consider the observation of diffuse halos of light around the discs of spiral galaxies, as a probe of the interaction cross section between dark matter (DM) and photons. Using the galaxy M101 as an example, we show that for a scattering cross section at the level of 10^-23(m /GeV ) cm² or greater dark matter in the halo will scatter light out from the more luminous center of the disc to larger radii, contributing to an effective increased surface brightness at the edges of the observed area on the sky. This allows us to set an upper limit on the DM-photon cross section using data from the Dragonfly instrument. We then show how to improve this constraint, and the potential for discovery, by combining the radial profile of DM-photon scattering with measurements at multiple wavelengths. Observation of diffuse light presents a new and potentially powerful way to probe the interactions of dark matter with photons, a way that is complementary to existing searches.

Mots clés: 95.35.+d; 95.85.Kr; 98.62.Gq; Dark matter; Visible; Galactic halos; High Energy Physics - Phenomenology; Astrophysics - Cosmology and Nongalactic Astrophysics

Domaines: Planète et Univers [physics]

Jonathan H. Davis, Joseph Silk. Glow in the Dark Matter: Observing Galactic Halos with Scattered Light. Physical Review Letters, 2015, 114, ⟨10.1103/PhysRevLett.114.051303⟩. ⟨insu-03644758⟩