The Dynamics of Star Cluster Formation

Juan Farias

Poster -- Star-forming regions

We study the early dynamical evolution of star forming clusters, particularly focused on the effects of the formation timescale. The timescale for star cluster formation may be long compared to the dynamical time of the system, so that during this phase there can be significant dynamical evolution. This is the process we set out to model, here via direct N-body simulations, including realistic primordial binary fractions. Specifically, we explore how the dynamical evolution of forming clusters depends on the cluster formation timescale, as well as other assumptions that are generally needed for star formation subgrid models, such as degree of primordial mass segregation and binarity. This is a complementary approach to expensive star cluster formation simulations that can not accurately follow the stellar dynamics (e.g. stellar binaries) during these early phases. We find that star clusters born slowly are able to virialize before exhausting/ejecting their natal gas and are more stable against expansion, independent of their initial density. Also, we are able to obtain a considerable amount of runaway stars even in low density environments, where as they do not form if star formation is fast. Stellar age gradients are also a natural outcome in our study with these gradients in agreement with observations only if the star formation dynamical timescale are long.