Diffuse interstellar bands in the near-infrared: Expanding the reddening range

TL;DR

This study expands the understanding of near-infrared diffuse interstellar bands by analyzing their behavior over a wider range of reddening, confirming strong correlations and revealing intrinsic profile variations, especially in the Galactic Centre environment.

Contribution

It provides new observational data on near-infrared DIBs across higher reddening levels and identifies intrinsic profile variations linked to formation processes and environmental factors.

Findings

Confirmed linear correlations between DIBs and reddening at higher values.

Detected intrinsic profile variations, including line broadening, especially in the Galactic Centre.

Discovered a new DIB candidate at 14795 Å in high reddening sightlines.

Abstract

We have investigated the behaviour of three strong near-infrared diffuse interstellar bands (DIBs) at {\lambda}13177 {\AA}, {\lambda}14680 {\AA}, and {\lambda}15272 {\AA}, on a larger sample of sightlines and over a wider range of extinctions than previously studied, utilizing spectra from three observatories. We applied two telluric correction techniques to reduce atmospheric contamination and have used Gaussian fits to characterise the DIB profiles and measure equivalent widths. We confirmed strong and approximately linear correlations with reddening of the {\lambda}13177 {\AA}, {\lambda}14680 {\AA} and {\lambda}15272 {\AA} DIBs, extending them to higher reddening values and strengthening their link to interstellar matter. Modelling of the {\lambda}14680 {\AA} DIB profiles revealed intrinsic variations, including line broadening, linked to their formation processes. This effect is particularly pronounced in the Galactic Centre (GC) environment, where multiple diffuse molecular clouds along the line of sight contribute to line broadening. We have detected one new DIB candidate at {\lambda}14795 {\AA} on sightlines with high reddening.