# Formation of Massive, Dense Cores by Cloud-Cloud Collisions

## TL;DR

This study uses high-resolution simulations to explore how cloud-cloud collisions in molecular clouds lead to the formation of dense cores, revealing the influence of collision velocity and cloud mass on core properties and implications for massive star formation.

## Contribution

It provides new insights into the effects of cloud mass and collision speed on core formation and the resulting core mass function, aligning with observed stellar initial mass functions.

## Key findings

- Slower collisions produce core mass functions with a power-law index of -1.6.
- Higher collision velocities increase early core formation but suppress subsequent core growth.
- The high-mass end of the core mass function follows a power law with index -2.3, similar to the stellar initial mass function.

## Abstract

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.