Disks no more: the morphology of low-mass simulated galaxies in FIREbox
Creators
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University of California, Riverside
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University of California, Davis
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3.
Pomona College
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Carnegie Observatories
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University of Zurich
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6.
California Institute of Technology
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University of California, Irvine
- 8. Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)
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Northwestern University
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Tel Aviv University
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California State Polytechnic University
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University of California, San Diego
Abstract
We study the morphology of hundreds of simulated central galaxies in the stellar mass range $M_\star =10^{7.5} \rm - 10^{11}~$$\rm M_\odot$ from the FIREbox cosmological volume. We demonstrate that FIREbox is able to predict a wide variety of morphologies, spanning from disk-dominated objects to spheroidal galaxies supported by stellar velocity dispersion. However, the simulations predict a strong relation between morphology (degree of rotational support) and stellar mass: galaxies comparable to the Milky Way are often disk-dominated while the presence of stellar disks mostly vanishes for dwarfs with M⋆ < 109 $\rm M_\odot$. This defines a "morphology transition" regime for galaxies with $10^9 <M_\star /\rm {M_\odot }< 10^{10}$ in which disks become increasingly common, but below which disks are rare. We show that burstiness in the star formation history and the deepening of the gravitational potential strongly correlate in our simulations with this transition regime, with disks forming in objects with lower levels of burstiness in the last ∼6 Gyr and halos with mass $\sim 10^{11} ~ \rm {M_{\odot }}$ and above. While observations support a transition towards thicker disks in the regime of dwarfs, our results are in partial disagreement with observations of at least some largely rotationally supported gas disks in dwarfs with M⋆ < 10⁹$\rm M_\odot$. This study highlights dwarf morphology as a fundamental benchmark for testing future galaxy formation models.
Copyright and License
Acknowledgement
The authors would like to thank Matthew Smith, Julio Navarro, and Simon White for insightful discussions that helped strengthen and improve the earliest versions of this draft. JAB and LVS are grateful for partial financial support from NSF CAREER-1945310 and NSF AST-2107993 grants. Some of the computations were performed using the computer clusters and data storage resources of the HPCC, which were funded by grants from NSF (MRI-2215705,MRI-1429826) and NIH (1S10OD016290-01A1). AW received support from NSF, via CAREER award AST-2045928 and grant AST-2107772. We acknowledge PRACE for awarding us access to MareNostrum at the Barcelona Supercomputing Center (BSC), Spain. This work was supported in part by a grant from the Swiss National Supercomputing Centre (CSCS) under project IDs s697 and s698. We acknowledge access to the Swiss National Supercomputing Centre, Switzerland, under the University of Zurich’s share with the project ID uzh18. JS was supported by a grant from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel. CRW thanks the generous contribution of the Cal Poly Pomona Department of Physics and Astronomy ICR and discretionary funds for summer research support.
Data Availability
This paper is based on snapshots, halo catalogues, and merger trees from the FIRE zoom-ins (P. F. Hopkins et al. 2014, 2018b) and FIREbox (R. Feldmann et al. 2023) data. Some public data are available at https://fire.northwestern.edu/. The FIRE-2 zoom-in simulations are publicly available (A. Wetzel et al. 2023) at FlatHUB. The main properties of the galaxy samples, and other products included in this analysis, may be shared upon request to the corresponding author if no further conflict exists with ongoing projects.
Files
staf1847.pdf
Additional details
Related works
- Is new version of
- Discussion Paper: arXiv:2508.00991 (arXiv)
Funding
- National Science Foundation
- 1945310
- National Science Foundation
- AST-2107993
- National Science Foundation
- AST-2045928
- National Science Foundation
- AST-2107772
- CSCS - Swiss National Supercomputing Centre
- United States-Israel Binational Science Foundation
Dates
- Submitted
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2025-08-01
- Accepted
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2025-10-19
- Available
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2025-10-24Published
- Available
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2025-12-05Corrected and typeset
Caltech Custom Metadata
- Caltech groups
- Astronomy Department , TAPIR , Walter Burke Institute for Theoretical Physics , Division of Physics, Mathematics and Astronomy (PMA) , Physics Department
- Publication Status
- Published