A Quantification of the Butterfly Effect in Cosmological Simulations and Implications for Galaxy Scaling Relations
Name
Genel_2019_ApJ_871_21.pdf
Description
Published version
Size
2.78 MB
Format
Adobe PDF
Checksum (MD5)
ebb0e1ce2503d8ad218a6ee53d4b24e2
Author(s)
Genel, Shy
Bryan, Greg L.
Springel, Volker
Hernquist, Lars
Nelson, Dylan
Pillepich, Annalisa
Weinberger, Rainer
Pakmor, Rüdiger
Marinacci, Federico
Vogelsberger, Mark
Date Issued
January 2019
Journal
Astrophysical Journal
Publisher
American Astronomical Society
Citation
Genel, Shy et al. "A Quantification of the Butterfly Effect in Cosmological Simulations and Implications for Galaxy Scaling Relations." Astrophysical Journal 871, 1 (January 2019): 21 © 2019 The American Astronomical Society
Version
Final published version
Abstract
We study the chaotic-like behavior of cosmological simulations by quantifying how minute perturbations grow over time and manifest as macroscopic differences in galaxy properties. When we run pairs of "shadow" simulations that are identical except for random minute initial displacements to particle positions (e.g., of order 10 -7 pc), the results diverge from each other at the individual galaxy level (while the statistical properties of the ensemble of galaxies are unchanged). After cosmological times, the global properties of pairs of "shadow" galaxies that are matched between the simulations differ from each other, generally at a level of ∼2-25%, depending on the considered physical quantity. We perform these experiments using cosmological volumes of (25-50 Mpc h)3 evolved either purely with dark matter, or with baryons and star formation but no feedback, or else using the full feedback model of the IllustrisTNG project. The runs cover four resolution levels spanning a factor of 512 in mass. We find that, without feedback, the differences between shadow galaxies generally become smaller as the resolution increases-but with the IllustrisTNG model, the results mostly converge toward a "floor. " This hints at the role of feedback in setting the chaotic properties of galaxy formation. Importantly, we compare the macroscopic differences between shadow galaxies to the overall scatter in various galaxy scaling relations, and conclude that, for the star formation-mass and the Tully-Fisher relations, the butterfly effect in our simulations contributes significantly to the overall scatter. We find that our results are robust to whether random numbers are used in the subgrid models or not. We discuss the implications for galaxy formation theory in general and for cosmological simulations in particular.
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.3847/1538-4357/aaf4bb
