Filamentary Hierarchies and Superbubbles. II. Impact of Superbubbles and Galactic Dynamics on Filament Formation and Fragmentation

Large-scale phenomena in spiral galaxies such as shear, supernovae, and magnetic fields all contribute to the formation and subsequent evolution of filamentary structure and star formation within them. In this paper, we analyze the properties and dynamics of filaments in a simulated Milky Way–like galaxy from B. Zhao et al. Using filament and superbubble structure analysis codes, we investigate the roles of Galactic shear, supernovae, superbubbles, and magnetic fields on the stability and fragmentation of filaments. We find that local shear has little effect on filament stability and the largest structures at outer radii of the disk may be more likely to be dissipated by shear than supernovae. Filaments are largely parallel to the magnetic field, which plays a significant role in filament stability. By measuring the ratio of surface pressure on a filament to that on its central spine, χf = Psurf/Pcentral, we find that filaments with χf ≤ 1 are dominated by their own self-gravity and have a strong tendency to be gravitationally supercritical, whereas those with χf > 1 are either transitory or in the act of being formed. Finally, we investigate the role of interstellar medium pressure on filament dynamics and stability as a function of Galactic radius, finding considerable changes in filament stability and the accompanying star formation rates in the inner versus outer regions of the disk.