# A Principal component analysis of the diffuse interstellar bands

## TL;DR

This study applies principal component analysis to 23 interstellar parameters, revealing that four main factors explain most variations, with implications for understanding the environment of diffuse interstellar bands.

## Contribution

It introduces a PCA approach to analyze interstellar parameters, identifying key factors influencing diffuse interstellar bands and their environmental dependencies.

## Key findings

- Four principal components explain 93% of the variation.
- The first component correlates with DIB-producing material.
- The second component relates to UV radiation levels.

## Abstract

We present a principal component analysis of 23 line of sight parameters (including the strengths of 16 diffuse interstellar bands, DIBs) for a well-chosen sample of single-cloud sightlines representing a broad range of environmental conditions. Our analysis indicates that the majority ($\sim$93\%) of the variations in the measurements can be captured by only four parameters The main driver (i.e., the first principal component) is the amount of DIB-producing material in the line of sight, a quantity that is extremely well traced by the equivalent width of the $\lambda$5797 DIB. The second principal component is the amount of UV radiation, which correlates well with the $\lambda$5797/$\lambda$5780 DIB strength ratio. The remaining two principal components are more difficult to interpret, but are likely related to the properties of dust in the line of sight (e.g., the gas-to-dust ratio). With our PCA results, the DIBs can then be used to estimate these line of sight parameters.