Pixel distribution of the S/N maps in all six fields (left) and distributions of the noise ratios between the noise estimated from the “individual” and “fixed” methods (right). The S/N map was obtained by dividing the science map and the typical 1σ noise in each field. The vertical dashed line in the left panel shows the adopted 4σ threshold during the source extraction. The noise ratio results from SEP, AEGEAN, and SOFIA are shown in yellow, blue, and green. The vertical dashed lines mark the median value from the corresponding ratio distributions. The median noise ratios of SEP and AEGEAN are very close and overlapped, around 0.984.