Forecast of cosmological parameters from peak counts in a 100 deg² survey at Euclid depth without tomography. Marginalized 2D (1 and 2σ contours) and 1D (full likelihood) constraints are displayed in blue for the DM-only case and in green when including baryon physics. Dashed lines correspond to the 1σ constraints in the 1D marginalized likelihood. The blue and green crosses indicate the best estimate in the 2D constraints, while the red crosses and lines indicate the input cosmological parameter values. Gray crosses correspond to parameters of the 25 cosmo-SLICS simulations that are used to estimate the cosmology dependence of the number of peaks.