Identification of New Near-Infrared DIBs in the Orion Nebula

TL;DR

This study identifies new near-infrared diffuse interstellar bands in the Orion Nebula, supporting the hypothesis that C_60^+ molecules contribute to these features, with implications for understanding complex molecules in space.

Contribution

The paper reports the discovery of three new C_60^+ candidate DIBs in the near-infrared, expanding knowledge of interstellar molecules and their spectral signatures.

Findings

Three new DIBs at ~9017A, 9210A, and 9258A identified as C_60^+ candidates

DIB profiles are asymmetric and similar to known C_60^+ features

Relative DIB strengths differ from laboratory measurements, indicating environmental effects

Abstract

Large organic molecules and carbon clusters are basic building blocks of life, but their existence in the universe has not been confirmed beyond doubt. A number of unidentified absorption features (arising in the diffuse inter-stellar medium), usually called ``Diffuse Inter-stellar Bands (DIBs)'', are hypothesized to be produced by large molecules. Among these, buckminsterfullerene C_60 has gained much attention as a candidate for DIB absorbers because of its high stability in space. Two DIBs at ~9577A and 9632A have been reported as possible features of C_60^+. However, it is still not clear how their existence depends on their environment. We obtained high-resolution spectra of three stars in/around the Orion Nebula, to search for any correlations of the DIB strength with carrier's physical conditions, such as dust-abundance and UV radiation field. We find three DIBs at ~9017A, 9210A, and 9258A as additional C_60^+ feature candidates, which could support this identification. These DIBs have asymmetric profiles similar to the longer wavelength features. However, we also find that the relative strengths of DIBs are close to unity and differ from laboratory measurements, a similar trend as noticed for the 9577/9632 DIBs.