Dust diffusion in SPH simulations of an isolated galaxy

TL;DR

This paper models dust grain size evolution in galaxy simulations, showing that including turbulence-driven diffusion improves agreement with observed dust extinction properties.

Contribution

It introduces a subgrid diffusion model for dust and metals in galaxy simulations, enhancing the realism of grain size distribution evolution.

Findings

Diffusion increases small grain production.

Improved match to Milky Way extinction curve.

Addresses previous biases in grain size distribution.

Abstract

We compute the evolution of the grain size distribution (GSD) in a suite of numerical simulations of an isolated Milky-Way-like galaxy using the $N$-body/smoothed-particle-hydrodynamics code {\sc Gadget-4}. The full GSD is sampled on a logarithmically spaced grid with 30 bins, and its evolution is calculated self-consistently with the hydrodynamical and chemical evolution of the galaxy using a state-of-the-art star formation and feedback model. In previous versions of this model, the GSD tended to be slightly biased towards larger grains and the extinction curve had a tendency to be flatter than the observations. This work addresses these issues by considering the diffusion of dust and metals through turbulence on subgrid scales and introducing a multi-phase subgrid model that enables a smoother transition from diffuse to dense gas. We show that diffusion can significantly enhance the production of small grains and improve the agreement with the observed dust extinction curve in the Milky Way.