Comparison of the determination of a detection between levels of signal to noise ratio in debiased polarization degree in blue for 3 − σ_P (dashed line) and 4 − σ_P (solid line) with the Stokes Q and U fluxes confidence level defined in Eq. A.2 in red. The gray contour and position are the 99% confidence level and best guess for the position of the center of emission by minimizing Eq. B.1.