The crystalline fraction of interstellar silicates in starburst galaxies

TL;DR

This paper models the evolution of silicate crystallinity in starburst galaxies, considering stellar dust production, amorphisation, and destruction, and finds that observed crystallinity levels suggest additional sources beyond stellar ejecta.

Contribution

It introduces a comprehensive model linking stellar population evolution to silicate crystallinity, highlighting the role of supernovae and the need for extra crystalline sources.

Findings

Detectable crystalline silicates may form at high star formation rates.

Crystallinity levels of 6.5-13% are observed in starburst galaxies.

Additional crystalline sources, like Active Galactic Nuclei, are implied.

Abstract

We present a model using the evolution of the stellar population in a starburst galaxy to predict the crystallinity of the silicates in the interstellar medium of this galaxy. We take into account dust production in stellar ejecta, and amorphisation and destruction in the interstellar medium and find that a detectable amount of crystalline silicates may be formed, particularly at high star formation rates, and in case supernovae are efficient dust producers. We discuss the effect of dust destruction and amorphisation by supernovae, and the effect of a low dust-production efficiency by supernovae, and find that when taking this into account, crystallinity in the interstellar medium becomes hard to detect. Levels of 6.5-13% crystallinity in the interstellar medium of starburst galaxies have been observed and thus we conclude that not all these crystalline silicates can be of stellar origin, and an additional source of crystalline silicates associated with the Active Galactic Nucleus must be present.