%0 Generic %1 li2017cluster %A Li, Hui %A Gnedin, Oleg Y. %A Gnedin, Nickolay Y. %D 2017 %K cluster efficiency formation simulations %T Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback %U http://arxiv.org/abs/1712.01219 %X The implementation of star formation and stellar feedback in cosmological simulations plays a critical role in shaping the properties of model galaxies. In the first paper of the series, we presented a new method to model star formation as a collection of star clusters. Here, we improve the algorithm by eliminating accretion gaps, increasing spatial resolution, and boosting momentum feedback. We also introduce the sub-grid initial bound fraction, $f_i$, that distinguishes cluster mass from stellar particle mass. We perform simulations with different star formation efficiency per free-fall time $\epsilon_ff$ and intensity of supernova momentum feedback $f_\rm boost$. 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, $f_\rm boost\approx5$. On the other hand, changing $\epsilon_ff$ from a few percent to 200% has little effect on the global galaxy properties. However, on smaller scales, the properties of star clusters are very sensitive to $\epsilon_ff$. We find that $f_i$ increases with $\epsilon_ff$ and cluster mass. Through the dependence on $f_i$, the shape of the cluster initial mass function also varies strongly with $\epsilon_ff$. The galactic environment controls the formation of massive clusters: 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 $\epsilon_ff$. The cluster formation timescale systematically decreases with increasing $\epsilon_ff$. Local variations in the gas accretion history lead to a one-sigma scatter of 0.25 dex for the integral efficiency of cluster formation. Joint constraints from all the observables prefer the runs that produce the median integral efficiency of 16%.

@misc{li2017cluster, abstract = {The implementation of star formation and stellar feedback in cosmological simulations plays a critical role in shaping the properties of model galaxies. In the first paper of the series, we presented a new method to model star formation as a collection of star clusters. Here, we improve the algorithm by eliminating accretion gaps, increasing spatial resolution, and boosting momentum feedback. We also introduce the sub-grid initial bound fraction, $f_i$, that distinguishes cluster mass from stellar particle mass. We perform simulations with different star formation efficiency per free-fall time $\epsilon_{\rm ff}$ and intensity of supernova momentum feedback $f_{\rm boost}$. 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, $f_{\rm boost}\approx5$. On the other hand, changing $\epsilon_{\rm ff}$ from a few percent to 200% has little effect on the 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 also varies strongly with $\epsilon_{\rm ff}$. The galactic environment controls the formation of massive clusters: 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 one-sigma scatter of 0.25 dex for the integral efficiency of cluster formation. Joint constraints from all the observables prefer the runs that produce the median integral efficiency of 16%.}, added-at = {2017-12-05T09:38:49.000+0100}, author = {Li, Hui and Gnedin, Oleg Y. and Gnedin, Nickolay Y.}, biburl = {https://www.bibsonomy.org/bibtex/27657ebd4754850f55220650a772451e7/miki}, description = {[1712.01219] Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback}, interhash = {284cc7f60832cc09dd31ce905403e56a}, intrahash = {7657ebd4754850f55220650a772451e7}, keywords = {cluster efficiency formation simulations}, note = {cite arxiv:1712.01219Comment: 18 pages, 14 figure., Submitted to AAS Journals}, timestamp = {2017-12-05T09:38:49.000+0100}, title = {Star Cluster Formation in Cosmological Simulations. II. Effects of Star Formation Efficiency and Stellar Feedback}, url = {http://arxiv.org/abs/1712.01219}, year = 2017 }