Astrophys. J., 861, 107-107 (2018/July-2)
Star cluster formation in cosmological simulations. II. Effects of star formation efficiency and stellar feedback.
LI H., GNEDIN O.Y. and GNEDIN N.Y.
Abstract (from CDS):
The implementation of star formation and stellar feedback in cosmological simulations plays a critical role in shaping galaxy properties. In the first paper of the series, we presented a new method to model star formation as a collection of star clusters. In this paper, we improve the algorithm by eliminating accretion gaps, boosting momentum feedback, and introducing a subgrid initial bound fraction, fi, that distinguishes cluster mass from stellar particle mass. We perform a suite of simulations with different star formation efficiency per freefall time εff and supernova momentum feedback intensity fboost. We find that the star formation history of a Milky Way-sized galaxy is sensitive to fboost, which allows us to constrain its value, fboost~5, in the current simulation setup. Changing εff from a few percent to 200% has little effect on global galaxy properties. However, on smaller scales, the properties of star clusters are very sensitive to εff. We find that fi increases with εff and cluster mass. Through the dependence on fi, the shape of the cluster initial mass function varies strongly with εff. The fraction of clustered star formation and maximum cluster mass increase with the star formation rate surface density, with the normalization of both relations dependent on εff. The cluster formation timescale systematically decreases with increasing εff. Local variations in the gas accretion history lead to a 0.25 dex scatter for the integral cluster formation efficiency. Joint constraints from all the observables prefer the runs that produce a median integral efficiency of 16%.
© 2018. The American Astronomical Society. All rights reserved.
galaxies: formation - galaxies: high-redshift - galaxies: star clusters: general - galaxies: star formation - methods: numerical
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