TS residual map above 1 GeV in the 2° × 2° region near W40, with pixel size corresponding to 0.05° × 0.05°, smoothed with a Gaussian filter of 0.45°. The square marks the best-fit central position of the assumed uniform disk used for spatial analysis, and the dashed circle with a radius of 0.46° shows its size. The diamond indicates the radio position of W40, and the small circle with a radius of 0.042° marks the core of the Serpens South Cluster (Gutermuth et al. 2008). The “+” indicate the point sources listed in the 4FGL, and excluded in our background model. The “×” symbol shows pulsars located close to W40 region in projection on the sky.