Dependence of the first core properties on initial cloud mass. Panel a: mean first core radius (mean radius is calculated over the time from the onset of the first core formation until the second core formation). The vertical lines span the minimum to maximum first core radius as the core evolves. Panel b: first core mass. Panel c: outer shock temperature as a function of initial cloud mass as estimated at a time after the second core formation when the first core is stable and no longer evolves. A transition region is seen around 8–10 M_⊙ indicating the diminishing first core radius and mass towards the high-mass regime.