Vertical structure of interstellar dust in the Milky Way

ABSTRACT Interstellar dust plays a central role in the evolution of galaxies by shaping star formation, altering observed stellar properties, and redistributing radiation across the electromagnetic spectrum. In the Milky Way, dust is concentrated in the Galactic disc and often associated with large-scale structures such as spiral arms and molecular clouds. Here, we present a detailed analysis of the vertical distribution and sub-structure of interstellar dust using a sample of approximately 23 million stars from literature with high-precision extinction measurements. We derive three-dimensional dust density profiles along various sightlines and fit vertical dust distributions using both single and double exponential disc models across 12 Galactocentric radial bins from $\sim$6 to $\sim$12 kpc. We show that a two-component disc model – comprising a ‘thin’ and a ‘thick’ dust disc – provides a better fit to the vertical dust profile than a single exponential disc, as indicated by Bayesian Information Criterion comparisons. The thin and thick discs have average scale heights of $81.0 \pm 6.7$ and $152.0 \pm 7.0$ pc, respectively. Our results also identify significant dust sub-structures, which align well with known spiral arms, molecular clouds, and star-forming regions.