  We investigate the influence of the turbulence forcing on the mass
distributions of gravitationally unstable cores by postprocessing data from
simulations of non-selfgravitating isothermal supersonic turbulence with
varying resolution. In one set of simulations solenoidal forcing is applied,
while the second set uses purely compressive forcing to excite turbulent
motions. From the resulting density field, we compute the mass distribution of
gravitationally unstable cores by means of a clump-finding algorithm. Using the
time-averaged probability density functions of the mass density, semi-analytic
mass distributions are calculated from analytical theories. We apply stability
criteria that are based on the Bonnor-Ebert mass resulting from the thermal
pressure and from the sum of thermal and turbulent pressure. Although there are
uncertainties in the application of the clump-finding algorithm, we find
systematic differences in the mass distributions obtained from solenoidal and
compressive forcing. Compressive forcing produces a shallower slope in the
high-mass power-law regime compared to solenoidal forcing. The mass
distributions also depend on the Jeans length resulting from the choice of the
mass in the computational box, which is freely scalable for non-selfgravitating
isothermal turbulence. Provided that all cores are numerically resolved and
most cores are small compared to the length scale of the forcing, the
normalised core mass distributions are found to be close to the semi-analytic
models. Especially for the high-mass tails, the Hennebelle-Chabrier theory
implies that the additional support due to turbulent pressure is important.
