Publication Date

6-22-2026

Document Type

Article

Publication Title

Astrophysical Journal

Volume

1005

Issue

1

DOI

10.3847/1538-4357/ae7349

Abstract

The recent “bullet-dwarf” model proposes that high-velocity collisions between dwarf galaxies can produce stellar systems with overluminous globular clusters (GCs) and a deficiency of dark matter, as observed in the NGC 1052 group galaxies NGC 1052-DF2 and NGC 1052-DF4. We present a possible analog system in the outskirts of the Fornax cluster: the ultradiffuse galaxy FCC 224 and its close companion FCC 240. Using deep Very Large Telescope/MUSE integral field spectroscopy, we characterize their stellar populations, internal kinematics, and GC systems to test this formation scenario. Both galaxies exhibit low velocity dispersions. Interpreted with a standard mass estimator at the half-light radius, and allowing for the known limitations associated with flattened systems, their inner dynamics are more naturally explained by stars alone than by either cuspy or cored dark matter halos. Both systems host unusually luminous GCs, closely resembling the top-heavy GC luminosity function of the NGC 1052 pair. Moreover, FCC 224 and FCC 240 are coeval with each other, with mass-weighted stellar ages of ∼10 Gyr, and their GC populations share similarly old ages, in agreement with predictions of the formation scenario. Despite these similarities, FCC 224 and FCC 240 form a much tighter system than DF2 and DF4, with a projected separation of 75 kpc (compared to 240 kpc) and a relative velocity of only 16 km s−1 (compared to 358 km s−1). This distinct configuration may suggest a different present-day manifestation of the same general class of galaxies and provides additional observational constraints on models of their formation and evolution.

Funding Number

DP250101673

Funding Sponsor

Space Telescope Science Institute

Keywords

Dark matter (353), Dwarf galaxies (416), Globular star clusters (656)

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Physics and Astronomy

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