2016/06/30 by Moupiya Maji, Qirong Zhu, Yuexing Li +3 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aa7aa1
Accepted in ApJ. 16 pages, 9 figures
arxiv created 2017/06/30 · arxiv updated 2017/08/02
Observations of globular clusters show that they have universal lognormal mass functions with a characteristic peak at ∼ 2× 105 \rmM\odot, but the origin of this peaked distribution is highly debated. Here we investigate the formation and evolution of star clusters in interacting galaxies using high-resolution hydrodynamical simulations performed with two different codes in order to mitigate numerical artifacts. We find that massive star clusters in the range of ∼ 105.5 - 107.5 \rmM\odot form preferentially in the highly-shocked regions produced by galaxy interactions. The nascent cluster-forming clouds have high gas pressures in the range of P/k ∼ 108 - 1012 \rmK \rmcm-3, which is ∼ 104 - 108 times higher than the typical pressure of the interstellar medium but consistent with recent observations of a pre-super star cluster cloud in the Antennae Galaxies. Furthermore, these massive star clusters have quasi-lognormal initial mass functions with a peak around ∼ 106 \rmM\odot. The number of clusters declines with time due to destructive processes, but the shape and the peak of the mass functions do not change significantly during the course of galaxy collisions. Our results suggest that gas-rich galaxy mergers may provide a favorable environment for the formation of massive star clusters such as globular clusters, and that the lognormal mass functions and the unique peak may originate from the extreme high-pressure conditions of the birth clouds and may survive the dynamical evolution.