Ratio of the time it takes in each run until the first core is formed (t_core1) to various collapse time estimates, as a function of ϵ. The blue squares represent the free-fall time computed using the cloud’s inital central density ρ_c (t_ff1), while the green triangles show the results from an alternate definition of the free-fall time based on the cloud’s average density (t_ff2). The black stars represent the cloud’s initial sound crossing time (t_sound). Finally, the best estimate is obtained with a modified version of t_ff1 which takes into account how unstable the cloud initially is to gravitational collapse by introducing the ϵ parameter (t_ff3).