We investigate the dynamical evolution of star clusters during their formation , assuming that they are born from a turbulent starless clump of a given mass that is embedded within a parent self-gravitating molecular cloud characterized by a particular mass surface density .
In contrast to the standard practice of most N -body studies , we do not assume that all stars are formed at once .
Rather , we explore the effects of different star formation rates on the global structure and evolution of young embedded star clusters , also considering various primordial binary fractions and mass segregation levels .
Our fiducial clumps studied in this paper have initial masses of M _ { cl } = 3000 M _ { \odot } , are embedded in ambient cloud environments of \Sigma _ { cloud } = 0.1 and 1 g cm ^ { -2 } , and gradually form stars with an overall efficiency of 50 % until the gas is exhausted .
We investigate star formation efficiencies per free-fall time in the range \epsilon _ { ff } = 0.01 to 1 , and also compare to the instantaneous case ( \epsilon _ { ff } = \infty ) of Paper I .
We show that most of the interesting dynamical processes that determine the future of the cluster , happen during the early formation phase .
In particular , the ejected stellar population is sensitive to the duration of star cluster formation : for example , clusters with longer formation times produce more runaway stars , since these clusters remain in a dense state for longer , thus favouring occurrence of dynamical ejections .
We also show that the presence of radial age gradients in star clusters depends sensitively on the star formation efficiency per free fall time , with observed values being matched best by our slowest forming clusters with \epsilon _ { ff } \lesssim 0.03 .