Variance (left panel), skewness (middle panel), and Kurtosis (right panel) of stacked spectra corresponding to “inside-” (black dots with red bars) and “outside feedback zones” (golden dots with blue bars) in Fig. 12 as a function of GLIMPSE 8 μm flux thresholds. The dots represent the median value and the bars span the 25–75 percentile spread of values from the 500 iterations for each threshold value.