Formation and evolution of young massive clusters in galaxy mergers: the SMUGGLE view

TL;DR

This study uses high-resolution galaxy merger simulations to explore how mergers influence the formation, properties, and evolution of young massive clusters, revealing increased formation efficiency and diverse survivability based on orbital dynamics.

Contribution

It provides new insights into the formation mechanisms and evolution of young massive clusters during galaxy mergers using detailed simulations with explicit star formation and feedback.

Findings

Higher dense gas fractions in mergers lead to more massive YMCs.

Cluster formation efficiency correlates with star formation rate surface density.

YMCs formed in tidal tails have higher survivability due to weaker tidal fields.

Abstract

Galaxy mergers are known to host abundant young massive cluster (YMC) populations, whose formation mechanism is still not well-understood. Here, we present a high-resolution galaxy merger simulation with explicit star formation and stellar feedback prescriptions to investigate how mergers affect the properties of the interstellar medium and YMCs. Compared with a controlled simulation of an isolated galaxy, the mass fraction of dense and high-pressure gas is much higher in mergers. Consequently, the mass function of both molecular clouds and YMCs becomes shallower and extends to higher masses. Moreover, cluster formation efficiency is significantly enhanced and correlates positively with the star formation rate surface density and gas pressure. We track the orbits of YMCs and investigate the time evolution of tidal fields during the course of the merger. At an early stage of the merger, the tidal field strength correlates positively with YMC mass, $\lambda_{\rm tid}\propto M^{0.71}$, which systematically affects the shape of the mass function and age distribution of the YMCs. At later times, most YMCs closely follow the orbits of their host galaxies, gradually sinking into the center of the merger remnant due to dynamical friction, and are quickly dissolved via efficient tidal disruption. Interestingly, YMCs formed during the first passage, mostly in tidal tails and bridges, are distributed over a wide range of galactocentric radii, greatly increasing their survivability because of the much weaker tidal field in the outskirts of the merger system. These YMCs are promising candidates for globular clusters that survive to the present day.