A High-Resolution Study of Near-Infrared Diffuse Interstellar Bands

TL;DR

This study uses high-resolution spectroscopy to analyze near-infrared diffuse interstellar bands, revealing their profiles, correlations with visual DIBs, and implications for their carriers across various interstellar sightlines.

Contribution

It provides detailed profile analysis and correlation studies of NIR DIBs, offering new insights into their characteristics and potential carriers compared to prior low-resolution observations.

Findings

NIR DIBs have asymmetric profiles well fitted by two Gaussian components.

The strength of NIR DIBs correlates with visual extinction A(V).

No notable correlation between NIR DIBs and aliphatic dust absorption features.

Abstract

We present high-resolution echelle spectroscopic observations of the two near- infrared (NIR) Diffuse Interstellar Bands (DIBs) at 13175 A and 11797.5 A. The DIBs have been observed in a number of diffuse interstellar medium sightlines that exhibit a wide range of visual extinctions. Band profiles are similar to those seen in narrow DIBs, clearly asymmetric and can be closely fitted in most cases using two simple Gaussian components. Gaussian fits were generally found to be more successful than fits based on a multiple-cloud model using a template DIB profile. For a sample of 9 objects in which both bands are observed, the strength of both NIR DIBs generally increases with A(V), and we report a correlation between the two observed bands over a large A(V) range and widely-separated lines of sight. The strength of the two bands is also compared against those of two visual DIBs and the diffuse ISM aliphatic dust absorption feature at 3.4 microns previously detected in the same sightlines. We find that the NIR DIBs do not exhibit notable (anti)correlations with either. Implications of these observations on possible DIB carrier species are discussed.