Indirect search for dark matter in M 31 with the CELESTE experiment

Context: .If dark matter is made of neutralinos, annihilation of such Majorana particles should produce high energy cosmic rays, especially in galaxy halo high density regions like galaxy centres. Aims: .M 31 (Andromeda) is our nearest neighbour spiral galaxy, and both its high mass and its low distance make it a source of interest for the indirect search for dark matter through γ-ray detection. Methods: .The ground based atmospheric Cherenkov telescope CELESTE observed M 31 from 2001 to 2003, in the mostly unexplored energy range 50-500 GeV. Results: .These observations provide an upper limit on the flux above 50 GeV around 10-10 cm-2 s-1 in the frame of supersymmetric dark matter, and more generally on any gamma emission from M 31.