2D histogram of the reduced χ² of the SED fitting as a function of the temperature T_c (see Sect. 4.1) for the photometrically reliable catalogue. The contours represent the 90%, 75%, 25%, 5% and 1% levels of the maximum of the 2D histogram over the (χ², T_c) space. Case 1 (black solid line): reduced χ² obtained for β = 2 as a function of the temperature inferred from the fit. When temperature becomes lower, more objects have a larger χ². Case 2 (red dashed line): reduced χ² as a function of the temperature obtained with a free β. The threshold χ² = 2 (dash-dotted blue line) indicates the maximum level of χ² that ensures a reasonable fit.