Filter functions w_ℓ (left) and g_ℓ (right) used in our toy model. For g_ℓ, all filters except the blue filter have g_ℓ = −8 for ℓ = 2, which is not shown in order to make the filters more visible for all other multipoles. The black lines show the filters that form the basis for the majority of results presented in the paper. The coloured filters are equal to the black filter for multipoles where the coloured filters are not visible. Red line: a smoother version of the main filter; green line: similar to the black filter but slightly simpler with no change of sign in g_ℓ; blue dashed line: highly simplified w_ℓ; red dashed line: the alternative model which filters the squared Gaussian map; blue line: filter used for the model with Gaussian white noise maps.