  In this paper, we examine whether clumpy, colliding, flows could be
responsible for the clump mass functions that have been observed in several
regions of embedded star formation, which have been shown to be described by a
Salpeter type slope. The flows presented here, which comprise a population of
initially identical clumps and the calculations are performed with and without
the inclusion of self-gravity. When the shock region is at its densest, we find
that the clump mass spectrum is always well modelled by a Salpeter type slope.
This is true regardless of whether the self-gravity is included in the
simulations or not. In the non-self-gravitating simulations, this slope is
retained at lower Mach numbers (Mach 5 and 10) as the simulations progress past
the densest phase. In the simulations which include self-gravity, we find that
low Mach number runs yield a flatter mass function after the densest phase.
This is simply a result of increased coagulation due to gravitational collapse
of the flows. In the high Mach number runs (Mach 20) the Salpeter slope is
always lost. The self gravitating calculations also show that the sub-group of
gravitationally bound clumps in which star formation occurs, always contain the
most massive clumps in the population. The mass function of these bound star
forming clumps is not at all similar to the Salpeter type mass function
observed for stars in the field. We conclude that the clump mass function may
not only have nothing to do with gravity, but also nothing to do with the star
formation process and the resulting mass distribution of stars. This raises
doubt over the claims that the clump mass function is the origin of the stellar
IMF, for regions such as rho Oph, Serpens and the Orion B cloud.

Astrophysics