Dark matter is called dark because it does not appear to interact with observable electromagnetic radiation, such as light, and is thus invisible to the entire electromagnetic spectrum, making it extremely difficult to detect using usual astronomical equipment. However, if dark matter particles interact even very weakly with the usual particles, their signals could still be observed. For example, in regions of high dark matter density (e.g., the centre of our galaxy) pairs of dark matter particles could annihilate to produce gamma rays, which are extremely energetic photons, with energies close to the 100 times of a mass of a proton.
Members of the CAC (Dr. G. Zaharijas and student C. Eckner) are part of two gamma-ray experiments, Fermi LAT and CTA. By analysing the astrophysical data they search for signals of dark matter, and have so far helped set constrains on particle physics models of the nature of dark matter particle and its interactions with the known particles.
Image credits: Illustris Collaboration/Illustris Simulation