Histograms of the residuals in the normalized S/N map, obtained using the NaCo data of TYC-8979-1683-1, inside four different annuli centered on the star: black solid lines are for an inner radius of 15 pixels (~5λ/D), purple solid lines for 50 pixels (~17λ/D), dark blue solid lines for 95 pixels (~32λ/D), and light blue solid lines for 247 pixels (~90λ/D). Each annulus has a width of 15 pixels except for the largest, which only has a width of 8 pixels. No obvious planetary-like signal can be found inside these annuli. Left: without filtering. Middle: with a pre-filtering, using F = 1/16. Right: with a pre-filtering, using F = 1/4. Gaussian fits of the histograms are overplotted in red dashed lines.