Cumulative contribution of different grain size intervals to the flux density from emitting dust located at 30 au from an M0-dwarf (grain temperature in Fig. 6). The Herschel/PACS observations of the DEBRIS survey reported in this paper were conducted at λ =100 and 160 µm. As supplementary information, curves are provided for the early surveys at λ =11 μm by Plavchan et al. (2005) and at λ =1200 μm by Lestrade et al. (2009). Flux density S_ν(a) integrated till grain size a is normalized by the total flux density F_tot integrated from minimum to maximum grain sizes of the plot.