Study of gamma-ray counterparts of IceCube high energy astrophysical neutrinos

IceCube has recently reported the discovery of high-energy neutrinos of astrophysical origin from an all-sky search. These are the highest energetic particles produced in interactions of cosmic rays ever detected, opening up the possibility to investigate the PeV (10¹⁵ eV) sky. Up to now, because of their low statistics and rather large positional uncertainties, these events have not been associated to any astrophysical source. We summarize here a search that resulted in plausible astronomical counterparts in the GeV - TeV bands. We also discuss the fact that various GeV powerful objects cannot be even assessed as possible counterparts due to their lack of TeV data. The definitive association between high-energy astrophysical neutrinos and the candidates singled out here will be significantly helped by more TeV observations but will be confirmed or disproved only by further upcoming IceCube observations.