Poissonian probability that the neutrino signal expected from the γ-ray observations are due to the fluctuations of the atmospheric neutrino background for 10 years exposure time with IceCube in the IC-79 configuration and a 2 degree region of interest around each longitude of the galactic plane (l), for the northern hemisphere (l ∈  [34:220] °). A line corresponding to the probability of 3σ has been added to help the readability. Key: in black, the probability using the spectral index computed with the Eq. (2); in grey, the uncertainties of the probability corresponding to 1σ.