Frequency spectra (black points with error bars) for thermal dust emission and AME compared, respectively, with DustEM and SpDust (dashed lines) for the diffuse ISM (top) and ionized gas (middle and bottom) regions within the Gould Belt. The solid line is the sum of the DustEM and SpDust models. The grey area in the top and middle panels corresponds to the  ± 1σ variations on the best-fit n_H values when fitting for a single phase. In the bottom panel we consider a mixture of two phases (n_H = 0.1cm^-3 and n_H = 55cm^-3, in the proportion of 46% and 54%, respectively), which marginally improves the fit for the ionized gas region at 23 GHz (the error is 0.3σ instead of 0.9σ ).