Correlation of feature A with published astrophysical components tracing interstellar matter. From top left to bottom right: (panel a) thermal dust component in logarithmic scaling (Planck Collaboration X 2016), (panel b) 2D histogram of the posterior mean intensity of feature A and the thermal dust component (mutual information I = 1.72, Pearson correlation coefficient ρ = 0.98), (panel c) hadronic component of the γ-ray spectrum in logarithmic scaling (Selig et al. 2015) with white pixels denoting missing values, (panel d) 2D histogram of the posterior mean intensity of feature A and the hadronic component (I = 1.22, ρ = 0.90). For the 2D histograms, the intensity ranges of the maps were divided into 256 equal bins and the number of intensity pairs per bin was displayed as counts on logarithmic scaling. Bright colors denote a high number of counts. Mutual information was calculated as described in Eq. (12) with 512 bins.