  We analyze the mass distribution of cores formed in an isothermal,
magnetized, turbulent, and self-gravitating nearly critical molecular cloud
model. Cores are identified at two density threshold levels. Our main results
are that the presence of self-gravity modifies the slopes of the core mass
function (CMF) at the high mass end. At low thresholds, the slope is shallower
than the one predicted by pure turbulent fragmentation. The shallowness of the
slope is due to the effects of core coalescence and gas accretion. Most
importantly, the slope of the CMF at the high mass end steepens when cores are
selected at higher density thresholds, or alternatively, if the CMF is fitted
with a log-normal function, the width of the lognormal distribution decreases
with increasing threshold. This is due to the fact that gravity plays a more
important role in denser structures selected at higher density threshold and
leads to the conclusion that the role of gravity is essential in generating a
CMF that bears more resemblance with the IMF when cores are selected with an
increasing density threshold in the observations.
