4 Discussion

It is perhaps important now to reiterate that we consider all computations in this Paper to be illustrative, not definitive. There are two fundamental reasons: a) the proper choices of input parameters and mass spectra are not yet known and b) our analysis implicitly assumes that most stars experience a few-body cluster decay governed primarily by point-mass dynamics. We can be assured that assumption (b) is wrong because the early dynamics of young stellar few-body systems must be affected by ongoing gas accretion (Bonnell et al. 1997, 1998) and possibly also by dissipative interactions with and between circumstellar disks (McDC95). In fact, a good deal of gas is present in observed young multiples that seem to be undergoing decay (Reipurth 2000). What we do show, however, is that, if a large fraction of stars form in small clusters, the imprint of a cluster total mass constraint through a two-step mass selection can, by itself, have a profound effect on mass-dependent properties of binary statistics. The difference in BF between one-step and two-step approaches is in fact larger near $M = M_{\odot}$ than that reported in McDC95 between one-step calculations which include strong disk collisions and those which do not. Imposition of our CMS $M_{\rm tot}$ constraint thus produces larger desirable shifts in the BF's than the introduction of strongly dissipative interactions in the cluster decay dynamics! Future, more complete observational determinations of BF(M) and q-distributions are on the horizon (see reviews in Zinnecker & Mathieu 2001) and should provide important diagnostics for binary formation mechanisms and contributing processes. A particular difficulty with few-body decay as a binary production mechanism is that brown dwarf binaries apparently exist (Basri 2001). Even with a two-step IMF, dynamical biasing causes the lightest masses in the final f_i to be preferentially single. If few-body decay is an important mechanism for star formation, then finding brown dwarf binaries to be common would suggest that brown dwarfs do not participate in the same few-body dynamics as young stars but must be formed by a separate mechanism. A possible alternative might be that the lower mass limit on the CMS effectively extends down to rather low masses. On the other hand, the BF of brown dwarfs is completely unknown. The so-called "brown dwarf desert'', i.e., the minimum in the companion mass function between the masses of low-mass stars and planets in radial velocity surveys (Halbwachs et al. 2000; Marcy et al. 2000), appears to be statistically significant and might well be an imprint of dynamical biasing (McDC93). At the same time, estimates for the population of apparently free-floating brown dwarfs in the field and in young clusters is growing dramatically with the advent of large-scale, highly sensitive photometric surveys (e.g., Reid 1999; Meyer et al. 2000).