Modelling dust extinction in the Magellanic Clouds

TL;DR

This paper models dust extinction in the Magellanic Clouds using a synthetic dust grain population, successfully explaining various observed extinction curves and highlighting the role of polycyclic aromatic hydrocarbons and classical grains.

Contribution

It extends a previous Milky Way dust model to the Magellanic Clouds, incorporating PAHs and classical grains to explain diverse extinction features.

Findings

Classical grains produce more extinction than PAHs in the Magellanic Clouds.

PAHs account for the non-linear far-UV rise in extinction curves.

A gap in classical grain size distribution correlates with PAH presence.

Abstract

We model the extinction profiles observed in the Small and Large Magellanic clouds with a synthetic population of dust grains consisting by core-mantle particles and a collection of free-flying polycyclic aromatic hydrocarbons. All different flavors of the extinction curves observed in the Magellanic Clouds can be described by the present model, that has been previously (successfully) applied to a large sample of diffuse and translucent lines of sight in the Milky Way. We find that in the Magellanic Clouds the extinction produced by classic grains is generally larger than absorption by polycyclic aromatic hydrocarbons. Within this model, the non-linear far-UV rise is accounted for by polycyclic aromatic hydrocarbons, whose presence in turn is always associated to a gap in the size distribution of classical particles. This hints either a physical connection between (e.g., a common cause for) polycyclic aromatic hydrocarbons and the absence of middle-sized dust particles, or the need for an additional component in the model, that can account for the non-linear far-UV rise without contributing to the UV bump at $\sim$217 nm, e.g., nanodiamonds.