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

Abstract

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 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) cm 2 or greater Dark Matter in the halo will scatter light out from the more luminous centre 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, which is complimentary to existing searches.

Spectral and Spatial Distortions of PeV Neutrinos from Scattering with Dark Matter

“…Our results are complimentary to bounds on DM-ν interactions at lower energies [5][6][7][8] and also to probes of scattering of e.g. DM with quarks [38][39][40], DM with electrons [41], DM with photons [42,43] and self-interactions [44], placing us closer than ever to understanding the nature of DM.…”

Probing Sub-GeV Mass Strongly Interacting Dark Matter with a Low-Threshold Surface Experiment

“…There is strong evidence that the majority of matter in the Universe is in the form of so-called dark matter (DM) [1], whose presence is inferred via its gravitational interactions with luminous matter (which makes up stars and galaxies), but which does not significantly scatter [2] or emit radiation. Since the luminous matter in the Universe is composed of particles, specifically those of the Standard Model, it is reasonable to assume that the dark matter is also made of particles, albeit of a so-far undiscovered species.…”

Axion Miniclusters: Formation, Structure and Observational Signatures

“…A complete microlensing calculation would also include the effect of the light source also having a finite size. However, as shown 18 It should be noted that using modern techniques, it is sometimes possible to resolve the individual images [184]. However, this is not significant for this work.…”

“…Generically, gravitational lensing creates additional images of the original source. In microlensing, the separation between these images is typically too small to resolve 18 . Instead, we observe the combined brightness of all of the images together.…”

“…We know that it must interact incredibly weakly with ordinary matter. For example, its cross-section with photons must be extremely small to explain why we haven't detected any radiation from DM yet [18][19][20][21]. Additionally, it must be stable on time scales of order the age of the universe since we know it must have already existed at z ≳ 10 5 , much earlier than the production of the CMB [22,23].…”