Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback
Abstract
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, f i , that distinguishes cluster mass from stellar particle mass. We perform a suite of simulations with different star formation efficiency per freefall time {ɛ }ff} and supernova momentum feedback intensity {f}boost}. We find that the star formation history of a Milky Way-sized galaxy is sensitive to {f}boost}, which allows us to constrain its value, {f}boost}≈ 5, in the current simulation setup. Changing {ɛ }ff} 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 {ɛ }ff}. We find that f i increases with {ɛ }ff} and cluster mass. Through the dependence on f i , the shape of the cluster initial mass function varies strongly with {ɛ }ff}. 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 {ɛ }ff}. The cluster formation timescale systematically decreases with increasing {ɛ }ff}. 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%.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2018
- DOI:
- 10.3847/1538-4357/aac9b8
- arXiv:
- arXiv:1712.01219
- Bibcode:
- 2018ApJ...861..107L
- Keywords:
-
- galaxies: formation;
- galaxies: high-redshift;
- galaxies: star clusters: general;
- galaxies: star formation;
- methods: numerical;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 18 pages, 14 figure., ApJ in press