Families and clusters of diffuse interstellar bands: a data-driven correlation analysis

ABSTRACT More than 500 diffuse interstellar bands (DIBs) have been observed in astronomical spectra, and their signatures correlations different environments studied over the past decades to reveal clues about nature of carriers. We compare equivalent widths DIBs, normalized amount reddening, EB-V, search for anticorrelated DIB pairs using a data sample containing 54 DIBs measured 25 sightlines. This covers most strong commonly detected optical region, sightlines probe variety medium conditions. find that 12.9 per cent are anticorrelated, lowest Pearson correlation coefficient is rnorm ? ?0.7. revisit correlation-based families able reproduce assignments such well-studied by applying hierarchical agglomerative k-means clustering algorithms. visualize dissimilarities between represented 1 ? rnorm, multidimensional scaling (MDS). With this representation, we form rather continuous sequence, which implies some properties carriers changing gradually following sequence. also at least two factors needed properly explain DIBs. While first factor may be interpreted as related ionization carriers, physical interpretation second less clear how interact with surrounding material.