Spiral arms across stellar populations in hydrodynamical simulations

Abstract

The majority of galaxies in the Local Universe are spiral galaxies. However, the formation and evolution of spiral arms is not well understood. Different theories explaining how spiral arms work give different predictions on their rotation and relative orientation between stellar populations. High-resolution hydrodynamical simulations with star formation are essential in providing predictions that can be compared with observations.

To better understand how spiral arms work, we analyse high-resolution simulations of an isolated disc galaxy. We quantify the presence of spiral arms adopting the method of the
local dimension, which was previously used in cosmological studies of filaments in the large scale structure of galaxies.

Using the local dimension, we study how the morphology of spiral arms differs between young and old stellar populations. In agreement with previous works, we find that the
spiral structure is most prominent in young stars and it weakens with growing age of stars. Despite this age dependence, both young and old populations show very similar patterns in the inner disc.