Toward understanding physical origin of 2175{\AA} extinction bump in interstellar medium

TL;DR

This paper proposes a new model suggesting that clusters of hydrogenated T-carbon molecules may be responsible for the 2175 Å UV extinction bump in the interstellar medium, fitting observed data with a mixture of materials.

Contribution

It introduces a mixture model involving HTC molecules and other dust components to explain the 2175 Å extinction feature, offering an alternative to previous theories.

Findings

The mixture model fits observed extinction curves of six stars.

Hydrogenated T-carbon molecules show a sharp absorption peak at 2175 Å.

The model provides an alternative explanation for the extinction bump's origin.

Abstract

The 2175 {\AA} ultraviolet (UV) extinction bump in interstellar medium (ISM) of the Milky Way was discovered in 1965. After intensive exploration of more than a half century, however, its exact origin still remains a big conundrum that is being debated. Here we propose a mixture model by which the extinction bump in ISM is argued possibly relevant to the clusters of hydrogenated T-carbon (HTC) molecules (C40H16) that have intrinsically a sharp absorption peak at the wavelength 2175 {\AA}. By linearly combining the calculated absorption spectra of HTC mixtures, graphite, MgSiO3 and Fe2SiO4, we show that the UV extinction curves of optional six stars can be nicely fitted. This present work poses an alternative explanation toward understanding the physical origin of the 2175 {\AA} extinction bump in ISM of the Milky Way.