Abstract:
Low surface brightness (LSB) galaxies have very diffuse, low surface density stellar discs that appear faint in optical images. They are very rich in neutral hydrogen (H I) gas, which extends well beyond the stellar discs. Their extended H I rotation curves and stellar discs indicate that they have very massive dark matter (DM) haloes compared to normal bright galaxies. Hence, LSB galaxies may represent valuable laboratories for the indirect detection of DM. In this paper, we search for weakly interacting massive particle annihilation signatures in four LSB galaxies and present an analysis of nearly 9 yr of data from the Fermi Large Area Telescope (Fermi-LAT). Above 500 MeV, no excess emission was detected from the LSB galaxies. We obtain constraints on the DM cross-section for different annihilation channels, for both individual and stacked targets. In addition to this, we use radio data from the Very Large Array radio telescope in order to derive DM constraints, following a multiwavelength approach. The constraints obtained from the four considered LSB galaxies are nearly three orders of magnitude weaker than the predicted limits for the thermal relic abundances and the combined limits achieved from Fermi-LAT observations of dwarf spheroidal galaxies. Finally, we discuss the possibility of detecting emission from LSB galaxies using the upcoming ground-based γ-ray and radio observatories, namely the Cherenkov Telescope Array and the Square Kilometre Array.
