Filaments and their role in the star formation process

speaker: Seamus Clarke


It has long been known that filaments have been connected to the star formation process but Herschel observations have sparked a recent interest in them. However, how they play this role is not fully understood, nor is the effect of their geometry on the star formation process. Here I will present two recent works, one numerical and one observational, looking at helping to understand the place filaments occupy in star formation. First, I will present a numerical study looking at the fragmentation of an accreting, non-equilibrium filament. I show that filaments are prone to fragment into smaller sub-filaments due to internal accretion-driven turbulence. These sub-filaments play a key role in the formation of cores, affecting both their number and mass. Moreover, unlike in equilibrium models of filament fragmentation, no characteristic fragmentation length-scale is observed. Second, I will present a Herschel study of the outer Galaxy giant molecular filament (GMF) G214.5-1.8. I find that G214.5 has a mass of ~16,000 solar masses, similar to clouds such as Serpens and Mon R2, yet is mostly quiescent while those are highly star forming. I find that G214.5 has fragmented into numerous clumps and that there appears to be no characteristic fragmentation length-scale present. I show that the GMF is unusual in its high aspect ratio, narrowness, and paucity of dense gas, as well as having a highly asymmetric radial profile consistent with compression. Using HI survey data, I find that G214.5 lies on the edge of a HI superbubble and this may be the cause of G214.5’s properties, highlighting external effects and how they shape filaments within the bubble-dominated interstellar medium.