Stacks at 250, 350, and 500 μm (from left to right) on MaDCoWS (a, b, c) and ACT cluster locations (d, e, f), as well as a set of random locations (g, h, i) in the H-ATLAS data set. See Sect. 5.2 for details. The x axis of each plot is aligned with RA, while the y axis is aligned with declination; both are in units of arcmin. The color bars are in units of MJy sr⁻¹. The red circles are 1.2′ in radius, the scale inside which we assigned excess flux density as being due to the cluster stack.