Unveiling the Milky Way dust extinction curve in 3D

TL;DR

This study maps the 3D variation of the Milky Way's dust extinction curve using spectra from 130 million stars, revealing insights into grain growth mechanisms and environmental effects on dust properties.

Contribution

It provides the first large-scale 3D map of the dust extinction curve in the Milky Way, significantly advancing understanding of dust grain evolution and properties.

Findings

Accretion dominates grain growth in moderate densities.

Coagulation is prevalent at higher densities.

Extinction curve flattens in star-forming regions.

Abstract

Interstellar dust is a major foreground contaminant for many observations and a key component in the chemistry of the interstellar medium, yet its properties remain highly uncertain. Using low-resolution spectra, we accurately measure the extinction curve - a diagnostic of the grain properties - for 130 million stars, orders of magnitude more than previously available, allowing us to map its variation in the Milky Way and Magellanic Clouds in 3D in unprecedented detail. We find evidence that accretion is the dominant mechanism of grain growth in moderately dense regions, with coagulation dominating at higher densities. Moreover, we find that the extinction curve flattens in star-forming regions, possibly caused by cycling of large grains formed in molecular clouds, or by preferential destruction of small grains by supernova shocks.