Maps of signal-to-noise ratio (left panels) and noise (σ_inst in mJy/beam, right panels) of the 1.2 mm N2CLS maps of the GOODS-N (upper panels) and COSMOS (lower panels) fields. The S/N maps and noise maps are matched filtered (see Sect. 2.3). The regions enclosed in the red contours (159 arcmin² for GOODS-N and 1010 arcmin² for COSMOS) have sufficiently low noise to be analyzed by our source-detection algorithm, and our catalogs and number counts are derived only in these areas (see Sects. 2.3 and 4).