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 disk 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 substructure 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 disk models across 12 Galactocentric radial bins from $\sim$6 to $\sim$12\,kpc. We show that a two-component disk model--comprising a ``thin'' and a ``thick'' dust disk--provides a better fit to the vertical dust profile than a single exponential disk, as indicated by Bayesian Information Criterion (BIC) comparisons. The thin and thick disks have average scale heights of $81.0 \pm 6.7$\,pc and $152.0 \pm 7.0$\,pc, respectively. Our results also identify significant dust substructures, which align well with known spiral arms, molecular clouds, and star-forming regions.