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Galaxies lacking dark matter produced by close encounters in a cosmological simulation


The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark-matter haloes, and that low-mass galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several cosmological simulations using the conventional model failed to form adequate numerical analogues with comparable internal characteristics (stellar masses, sizes, velocity dispersions and morphologies). Here we show that the standard paradigm naturally produces galaxies lacking dark matter with internal characteristics in agreement with observations. Using a state-of-the-art cosmological simulation and a meticulous galaxy-identification technique, we find that extreme close encounters with massive neighbours can be responsible for this. We predict that ~30% of massive central galaxies (with at least 1011 solar masses in stars) harbour at least one dark-matter-deficient satellite (with 108–109 solar masses in stars). This distinctive class of galaxies provides an additional layer in our understanding of the role of interactions in shaping galactic properties. Future observations surveying galaxies in the aforementioned regime will provide a crucial test of this scenario.

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Fig. 1: Galaxies lacking dark matter.
Fig. 2: Fraction of mass in dark matter in simulated and observed galaxies.
Fig. 3: Comparison of internal properties in simulated and observed galaxies.
Fig. 4: Conditions for creating a galaxy lacking dark matter.

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Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request, contingent on approval by the FIRE Collaboration on a case-by-case basis.

Code availability

The codes we used are available as follows: GIZMO,; yt,; AHF,; FIRE Studio,; WebPlotDigitizer, Python scripts used to create the Figs. 14 and Supplementary Figs. 19 are available from the corresponding author on reasonable request, contingent on approval by the FIRE Collaboration on a case-by-case basis.


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Sabbatical leave support from Pomona College and the Harry and Grace Steele Foundation (J.M.). NASA Hubble Fellowship grant number HST-HF2-51454.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract number NAS5-26555 (S.D.). NSF grant number AST-1910346 (J.S.B., F.J.M. and S.Y.). Swiss National Science Foundation grant numbers PP00P2_157591, PP00P2_194814 and 200021_188552; Swiss National Supercomputing (CSCS) project IDs s697 and s698 (R.F.). NSF Research Grant numbers 1911233 and 20009234, NSF CAREER grant number 1455342, NASA grant numbers 80NSSC18K0562 and HST-AR-15800.001-A (P.F.H.). NASA grant number 80NSSSC20K1469 (A.L.). Gary McCue postdoctoral fellowship through the Center for Cosmology at UC Irvine (Z.H.). National Science Foundation Graduate Research Fellowship under grant number DGE-1839285 (C.K.). NSF CAREER grant number 2045928; NASA ATP grant numbers 80NSSC18K1097 and 80NSSC20K0513; HST grant numbers AR-15809 and GO-15902 from STScI; Scialog Award from the Heising-Simons Foundation; Hellman Fellowship (A.W.). NSF grant number AST-2009687 and by the Flatiron Institute, which is supported by the Simons Foundation (D.A.-A.). NSF CAREER award number AST-1752913, NSF grant number AST-1910346, NASA grant numbers NNX17AG29G and HST-AR-15006, HST-AR-15809, HST-GO-15658, HST-GO-15901, HST-GO-15902, HST-AR-16159 and HST-GO-16226 from STScI (M.B.-K.). Simons Investigator Award from the Simons Foundation; NSF grant number AST-1715070 (E.Q.). NSF through grant numbers AST-1715216 and CAREER award AST-1652522; by NASA through grant number 17-ATP17-0067; by STScI through grant number HST-AR-16124.001-A; and by the Research Corporation for Science Advancement through a Cottrell Scholar Award and a Scialog Award (C.-A.F.-G.). NSF grant number AST-1715101 (D.K.). Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations FTA-HopkinsAST20016 supported by the NSF and TACC and NASA HEC SMD-16-7592. We acknowledge PRACE for awarding us access to MareNostrum at the Barcelona Supercomputing Center (BSC), Spain. This research was partly carried out via the Frontera computing project at the Texas Advanced Computing Center. Frontera is made possible by National Science Foundation award number OAC-1818253. We acknowledge access to Piz Daint at the Swiss National Supercomputing Centre, Switzerland under the University of Zurich’s share with the project ID uzh18. Additional computing support was provided by S3IT resources at the University of Zurich. We thank Y. Jing for patiently answering every question we had regarding their 2019 paper, and for sharing the data we requested. We also thank P. van Dokkum, J. Hudgings, D. Whitaker, D. Tanenbaum and R. Gaines for comments on an earlier draft, and C. Hayward for data-transfer support. J.M. thanks J.S.B., P.F.H., P. Torrey and L. Hernquist for sabbatical-leave hospitality. J.M. (an astronomer of Indigenous ancestry, non-Cherokee) thanks D. Ingram (a Cherokee physicist) for sharing knowledge about the Cherokee Nation and cultural appropriation. This work was conducted on Tongva-Gabrielino land.

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Authors and Affiliations



J.M. conducted the analysis and designed the manuscript, with substantial input from S.D. and J.S.B. S.D. collected observational data from the literature and verified the theory–observations comparisons. R.F. ran the cosmological simulation used in this work. O.Ç. generated the halo catalogues and merger trees. A.G. provided support for the creation of mock images. A.L. and C.B.H. provided support with yt. C.K. calculated g-band effective radii, Sérsic indices and surface brightness contours. C.K. and F.J.M. calculated stellar ages, metallicities and colours; and S.D. conducted the observational comparison. J.S.B., R.F., O.Ç. and F.J.M. worked on the discussion of numerical stripping, with substantial input from F.J. Z.H. contributed to the literature comparison. All authors contributed to the final creation of the manuscript and figures.

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Correspondence to Jorge Moreno.

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Supplementary Figs. 1–9, Tables 1–4 and Discussion.

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Moreno, J., Danieli, S., Bullock, J.S. et al. Galaxies lacking dark matter produced by close encounters in a cosmological simulation. Nat Astron 6, 496–502 (2022).

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