A Re-examination of UV Extinction and Diffuse Interstellar Bands

Lynne A. Valencic

Since their discovery in the 1930s, the diffuse interstellar bands (DIBs) and their carriers have proven to be enigmatic, but a concensus has been reached that the carriers are likely to be ionized polycyclic aromatic hydrocarbons (PAHs). Models of PAHs show that they should contribute strongly to UV extinction in the diffuse ISM, particularly the far-UV nonlinear rise. In order to gain a more comprehensive view of the relationships between PAHs and UV extinction carriers, we have assembled DIB strengths from the literature and combined it with our homogeneous database UV extinction characteristics. We considered 4 DIB features over more than 100 lines of sight, making it the largest sample studied up to this point. Our results will be useful in constraining models of UV extinction.