Diffuse Interstellar Bands: How Are They Related to Known Gas-Phase Constituents of the ISM?

TL;DR

This review examines how diffuse interstellar bands (DIBs) correlate with known gas-phase constituents of the interstellar medium, providing insights into their physical and chemical relationships and environmental dependencies.

Contribution

It compiles and analyzes correlations between DIBs and atomic/molecular species, highlighting how these relationships inform understanding of DIB carriers and their environmental variations.

Findings

Strong correlations between DIBs and certain atomic/molecular species.

Deviations reveal environmental influences on DIB strengths.

Profile variations relate to physical conditions in the ISM.

Abstract

In this brief review of recent work relating the DIBs to other gas-phase constituents of the ISM, we explore correlations between DIB equivalent widths and the column densities of various atomic and molecular species, drawn from a large database constructed for that purpose. The tightness and slopes of the correlations can provide information on how the DIBs might be related to those species (physically, chemically, spatially) and on various properties of the DIB carriers. Deviations from the mean relationships can reveal dependences of DIB strengths on other parameters, regional variations in DIB behavior, and individual sight lines where unusual environmental conditions affect the DIBs. Variations in DIB profiles (e.g., wings, substructure) and relative strengths may be related to differences in physical conditions inferred from atomic and/or molecular absorption lines.