Kavli Affiliate: Mark Vogelsberger
| First 5 Authors: Hui Li, Mark Vogelsberger, Greg L. Bryan, Federico Marinacci, Laura V. Sales
| Summary:
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.
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