Formation of Massive, Dense Cores by Cloud-Cloud Collisions
  We performed sub-parsec ($\sim$ 0.014 pc) scale simulations of cloud-cloud
collisions of two idealized turbulent molecular clouds (MCs) with different
masses in the range of $0.76 - 2.67 \times 10^4$M$_{\odot}$ and with collision
speeds of 5 $-$ 30 km/s. Those parameters are larger than Takahira, Tasker and
Habe (2014) (paper I) in which the colliding system showed a partial gaseous
arc morphology that supports the NANTEN observations of objects indicated to be
colliding MCs by numerical simulations. Gas clumps with density greater than
$10^{-20}$ g cm$^{-3}$ were identified as pre-stellar cores and tracked through
the simulation to investigate the effect of mass of colliding clouds and
collision speeds on the resulting core population. Our results demonstrate that
smaller cloud property is more important for results of cloud cloud collisions.
The mass function of formed cores can be approximated by a power law relation
with index $\gamma$ = -1.6 in slower cloud cloud collisions ($v \sim 5 $ km/s),
in good agreement with observation of MCs. A faster relative velocity increases
the number of cores formed in the early stage of collisions and shortens gas
accretion phase of cores in the shocked region, leading to suppression of core
growth. The bending point appears in the high mass part of the core mass
function and the bending point mass decreases with increasing of the collision
velocity for the same combination of colliding clouds. The high mass part of
the core mass function than the bending point mass can be approximated by a
power law with $\gamma$ = -2.3 that is very similar to the power index of the
massive part of the observed initial stellar mass function. We discuss
implication of our results for the massive star formation in our Galaxy.
