The impact of stellar bending waves on the star-forming gas layer

Abstract

Previous studies have shown that disc galaxies like the Milky Way are not necessarily “in a state of equilibrium . . . in the vertical direction” (Chequers, 2018). When a perturbation is applied to the vertical motions of stars, the stability of the stellar disc in the vertical direction allows for the formation of stellar bending waves. These waves result in a group of stars oscillating through the disc in a coherent manner, and may also manifest as warps in a galaxy’s stellar disc. However, the full consequences these bending waves have on the surrounding gas are unknown. The aim of this dissertation was to study the impact stellar bending waves have on the star-forming gas layer. To do so, two simulations – one warped and the other unwarped – were used to analyse the relationship between stars and surrounding gas in a disc galaxy. Khachaturyants et al. (2022) had previously confirmed the presence of stellar bending waves in these simulations’ stellar components. The present research confirms a correlation between the stellar and gaseous components of the unwarped model in relation to vertical perturbations. Our studies indicate that as the stellar disc is being perturbed due to the bending waves, there is an excitation of bending waves in the surrounding star-forming gas layer, which is then carried in the stars’ direction of motion. This research suggests that there is still much to learn about the impact of stellar bending waves on the star-forming gas layer and the consequences this has on the rest of the galaxy’s structure, dynamics, and evolution.