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Title: How Galaxies Form Stars: The Connection between Local and Global Star Formation in Galaxy Simulations

Abstract

Using a suite of isolated $$L_\star$$ galaxy simulations, we show that global depletion times and star-forming gas mass fractions in simulated galaxies exhibit systematic and well-defined trends as a function of the local star formation efficiency per freefall time, $$\epsilon_{\rm ff}$$, strength of stellar feedback, and star formation threshold. We demonstrate that these trends can be reproduced and explained by a simple physical model of global star formation in galaxies. Our model is based on mass conservation and the idea of gas cycling between star-forming and non-star-forming states on certain characteristic time scales under the influence of dynamical and feedback processes. Both the simulation results and our model predictions exhibit two limiting regimes with rather different dependencies of global galactic properties on the local parameters. When $$\epsilon_{\rm ff}$$ is small and feedback is inefficient, the total star-forming mass fraction, $$f_{\rm sf}$$, is independent of $$\epsilon_{\rm ff}$$ and the global depletion time, $$\tau_{\rm dep}$$, scales inversely with $$\epsilon_{\rm ff}$$. When $$\epsilon_{\rm ff}$$ is large or feedback is very efficient, these trends are reversed: $$f_{\rm sf} \propto \epsilon_{\rm ff}^{-1}$$ and $$\tau_{\rm dep}$$ is independent of $$\epsilon_{\rm ff}$$ but scales linearly with the feedback strength. We also compare our results with the observedmore » depletion times and mass fractions of star-forming and molecular gas and show that they provide complementary constraints on $$\epsilon_{\rm ff}$$ and the feedback strength. In conclusion, we show that useful constraints on $$\epsilon_{\rm ff}$$ can also be obtained using measurements of the depletion time and its scatter on different spatial scales.« less

Authors:
ORCiD logo [1]; ORCiD logo [1];  [2]
  1. The Univ. of Chicago, Chicago, IL (United States)
  2. The Univ. of Chicago, Chicago, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, 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)
OSTI Identifier:
1469371
Report Number(s):
arXiv:1803.00007; FERMILAB-PUB-18-365-A
Journal ID: ISSN 1538-4357; 1684463
Grant/Contract Number:  
AC02-07CH11359
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Volume: 861; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; galaxies: evolution; ISM: kinematics and dynamics; methods: numerical; stars: formation

Citation Formats

Semenov, Vadim A., Kravtsov, Andrey V., and Gnedin, Nickolay Y. How Galaxies Form Stars: The Connection between Local and Global Star Formation in Galaxy Simulations. United States: N. p., 2018. Web. doi:10.3847/1538-4357/aac6eb.
Semenov, Vadim A., Kravtsov, Andrey V., & Gnedin, Nickolay Y. How Galaxies Form Stars: The Connection between Local and Global Star Formation in Galaxy Simulations. United States. https://doi.org/10.3847/1538-4357/aac6eb
Semenov, Vadim A., Kravtsov, Andrey V., and Gnedin, Nickolay Y. Tue . "How Galaxies Form Stars: The Connection between Local and Global Star Formation in Galaxy Simulations". United States. https://doi.org/10.3847/1538-4357/aac6eb. https://www.osti.gov/servlets/purl/1469371.
@article{osti_1469371,
title = {How Galaxies Form Stars: The Connection between Local and Global Star Formation in Galaxy Simulations},
author = {Semenov, Vadim A. and Kravtsov, Andrey V. and Gnedin, Nickolay Y.},
abstractNote = {Using a suite of isolated $L_\star$ galaxy simulations, we show that global depletion times and star-forming gas mass fractions in simulated galaxies exhibit systematic and well-defined trends as a function of the local star formation efficiency per freefall time, $\epsilon_{\rm ff}$, strength of stellar feedback, and star formation threshold. We demonstrate that these trends can be reproduced and explained by a simple physical model of global star formation in galaxies. Our model is based on mass conservation and the idea of gas cycling between star-forming and non-star-forming states on certain characteristic time scales under the influence of dynamical and feedback processes. Both the simulation results and our model predictions exhibit two limiting regimes with rather different dependencies of global galactic properties on the local parameters. When $\epsilon_{\rm ff}$ is small and feedback is inefficient, the total star-forming mass fraction, $f_{\rm sf}$, is independent of $\epsilon_{\rm ff}$ and the global depletion time, $\tau_{\rm dep}$, scales inversely with $\epsilon_{\rm ff}$. When $\epsilon_{\rm ff}$ is large or feedback is very efficient, these trends are reversed: $f_{\rm sf} \propto \epsilon_{\rm ff}^{-1}$ and $\tau_{\rm dep}$ is independent of $\epsilon_{\rm ff}$ but scales linearly with the feedback strength. We also compare our results with the observed depletion times and mass fractions of star-forming and molecular gas and show that they provide complementary constraints on $\epsilon_{\rm ff}$ and the feedback strength. In conclusion, we show that useful constraints on $\epsilon_{\rm ff}$ can also be obtained using measurements of the depletion time and its scatter on different spatial scales.},
doi = {10.3847/1538-4357/aac6eb},
url = {https://www.osti.gov/biblio/1469371}, journal = {The Astrophysical Journal (Online)},
issn = {1538-4357},
number = 1,
volume = 861,
place = {United States},
year = {2018},
month = {6}
}

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    Works referencing / citing this record:

    The Gas–Star Formation Cycle in Nearby Star-forming Galaxies. I. Assessment of Multi-scale Variations
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