Diffuse interstellar bands and UV extinction curves. The missing link.

Abstract

The connection between diffuse interstellar bands and components of the interstellar ultraviolet extinction curve, decomposed according to the Fitzpatrick & Massa scheme, is analysed from new observations of several DIBs in the line of sight to 28 stars measured by IUE. We find that the strength of the 217.5nm bump positively correlates with DIB strength, whereas correlations with a negative slope exist with the FUV non-linear rise and the width of the bump. There is no correlation with linear rise. The relation of bump height versus DIB strength does not pass through zero. The results are interpreted within the polycyclic aromatic hydrocarbon (PAH) framework. They strengthen the hypothesis that the FUV non-linear rise is produced by neutral PAHs, whereas DIB carriers are found among some ionised or radical PAHs.