Stacked intensity estimates obtained from LinSimStack for individual COSMOS2020 bins, fit with a modified black-body emission continuum SED model. The top panels of each sub-figure show the stacked mean intensities (blue crosses) and corresponding 1σ envelope of the emcee fits (blue) for a subset of the catalog bins; the bottom panels show the signal-to-noise of the fit residuals. The vertical dashed line represents the wavelength cut, λ_cut, between the two piecewise components of the SED continuum model in Eq. (3) (i.e., the frequency ν₀). For a specific z interval, [CII]-158 μm emission is redshifted into a SPIRE band and manifests as excess residual emission over the continuum; these are marked in orange. The SPIRE 500 μm map contains redshifted [CII]-158 μm from the highest two z bins. Different rows and columns correspond to different stellar mass log(M/M_⊙) and redshift z cuts; all bins shown here are from the star-forming selection. The labels indicate the number count within a bin in the catalog and as predicted by the stellar mass function (SMF) from Weaver et al. (2023). We conservatively inflate the variance on the [CII]-158 μm residual emission by the reduced chi-squared, χ_r², statistic of each SED fit. The bottom row shows residuals obtained by adding over all bins at the same redshift interval, with potential [CII]-158 μm emission again marked in orange. For brevity, we only show stacking within the three highest stellar mass bins (for each redshift bin with potential [CII]-158 μm emission); these are the predominant contributors to the CIB and [CII]-158 μm emission. (See Appendix B for stacking results in all bins.) The bottom row shows the residuals obtained by adding all stellar mass and star-forming plus quiescent bins at a redshift.