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Title: Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback

Abstract

Here, 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 $$\epsilon_{\rm ff}$$ and supernova momentum feedback intensity $$f_{\rm boost}$$. We find that the star formation history of a Milky Way-sized galaxy is sensitive to $$f_{\rm boost}$$, which allows us to constrain its value, $$f_{\rm boost}\approx5$$, in the current simulation setup. Changing $$\epsilon_{\rm ff}$$ 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 $$\epsilon_{\rm ff}$$. We find that $$f_i$$ increases with $$\epsilon_{\rm ff}$$ and cluster mass. Through the dependence on $$f_i$$, the shape of the cluster initial mass function varies strongly with $$\epsilon_{\rm ff}$$. 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 $$\epsilon_{\rm ff}$$. The cluster formation timescale systematically decreases with increasing $$\epsilon_{\rm ff}$$. 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%.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3]
  1. Univ. of Michigan, Ann Arbor, MI (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Univ. of Chicago, Chicago, IL (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1469370
Report Number(s):
arXiv:1712.01219; FERMILAB-PUB-18-366-A
Journal ID: ISSN 1538-4357; 1684467
Grant/Contract Number:  
AC02-07CH11359
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 861; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; galaxies: formation; galaxies: high-redshift; galaxies: star clusters: general; galaxies: star formation; methods: numerical

Citation Formats

Li, Hui, Gnedin, Oleg Y., and Gnedin, Nickolay Y. Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback. United States: N. p., 2018. Web. doi:10.3847/1538-4357/aac9b8.
Li, Hui, Gnedin, Oleg Y., & Gnedin, Nickolay Y. Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback. United States. doi:10.3847/1538-4357/aac9b8.
Li, Hui, Gnedin, Oleg Y., and Gnedin, Nickolay Y. Tue . "Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback". United States. doi:10.3847/1538-4357/aac9b8. https://www.osti.gov/servlets/purl/1469370.
@article{osti_1469370,
title = {Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback},
author = {Li, Hui and Gnedin, Oleg Y. and Gnedin, Nickolay Y.},
abstractNote = {Here, 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 $\epsilon_{\rm ff}$ and supernova momentum feedback intensity $f_{\rm boost}$. We find that the star formation history of a Milky Way-sized galaxy is sensitive to $f_{\rm boost}$, which allows us to constrain its value, $f_{\rm boost}\approx5$, in the current simulation setup. Changing $\epsilon_{\rm ff}$ 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 $\epsilon_{\rm ff}$. We find that $f_i$ increases with $\epsilon_{\rm ff}$ and cluster mass. Through the dependence on $f_i$, the shape of the cluster initial mass function varies strongly with $\epsilon_{\rm ff}$. 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 $\epsilon_{\rm ff}$. The cluster formation timescale systematically decreases with increasing $\epsilon_{\rm ff}$. 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%.},
doi = {10.3847/1538-4357/aac9b8},
journal = {The Astrophysical Journal (Online)},
number = 2,
volume = 861,
place = {United States},
year = {2018},
month = {7}
}

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