Puzzling Ultra-Diffuse Galaxy Evolution (PUDGE). II. A transformation pathway from ultra-diffuse galaxies to compact dwarfs in galaxy clusters
Abstract
Ultra-diffuse galaxies (UDGs) and compact dwarfs (CDs) occupy opposite extremes of the structural parameter space of dwarf galaxies, yet their spatial distributions in clusters suggest a possible evolutionary connection. Observational studies have reported a pronounced anticorrelation between the two populations interpreted as evidence that CDs represent tidally stripped remnants of diffuse progenitors, a scenario that implicitly assumes a compact stellar nucleus must be present at infall to survive environmental processing. We tested this hypothesis using the IllustrisTNG cosmological simulation (TNG100) by examining the UDG and CD populations in seven galaxy clusters and tracing the evolutionary histories of 112 present-day CDs. We confirm that TNG100 reproduces the observed spatial anticorrelation, with CDs concentrated within d/R200 ≲ 0.2 and UDGs preferentially inhabiting the cluster outskirts. Tracing CDs back in time, we identified eight systems whose progenitors undergo a transient UDG phase, with extremely high gas fractions (fgas ≳ 0.8), immediately before cluster infall. In all eight systems, a vast majority of the present-day stellar mass was assembled after the epoch of maximum spatial extent, and the peak star formation rate during the transformation is the highest each galaxy achieves across its entire lifetime. The UDG progenitors show no prominent stellar cores before infall, demonstrating that the compact component of the resulting CD is not an exposed preexisting nucleus but is instead freshly built through starburst-driven star formation during the stripping process itself. Our results reveal a physically motivated UDG-to-CD transformation pathway driven entirely by cluster environment that is fundamentally distinct from classical tidal stripping scenarios and highlight the critical role of gas richness as a prerequisite for this channel.
Related
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- Characterising the formation and evolution of S0-galaxies (CaFES-0): Their formation pathways around galaxy clusters
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- Probing the dynamics of extreme galaxies. I. Dark matter content in ultra-diffuse galaxies
- The MIni-Halos in MIni-Clusters (MIMIC) project. New insights into the origin of mini-halos from a LOFAR, uGMRT, and MeerKAT study of diffuse radio emission in Abell 496 and ZwCl 235
BibTeX
@misc{pavlov2026puzzling,
title = {{Puzzling Ultra-Diffuse Galaxy Evolution (PUDGE). II. A transformation pathway from ultra-diffuse galaxies to compact dwarfs in galaxy clusters}},
author = {Nataša Pavlov and Ana Mitrašinović},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2605.24918},
eprint = {2605.24918},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.24918},
note = {CC BY-SA 4.0},
}
RIS
TY - UNPB
TI - Puzzling Ultra-Diffuse Galaxy Evolution (PUDGE). II. A transformation pathway from ultra-diffuse galaxies to compact dwarfs in galaxy clusters
AU - Nataša Pavlov
AU - Ana Mitrašinović
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2605.24918
UR - https://arxiv.org/abs/2605.24918
AB - Ultra-diffuse galaxies (UDGs) and compact dwarfs (CDs) occupy opposite extremes of the structural parameter space of dwarf galaxies, yet their spatial distributions in clusters suggest a possible evolutionary connection. Observational studies have reported a pronounced anticorrelation between the two populations interpreted as evidence that CDs represent tidally stripped remnants of diffuse progenitors, a scenario that implicitly assumes a compact stellar nucleus must be present at infall to survive environmental processing. We tested this hypothesis using the IllustrisTNG cosmological simulation (TNG100) by examining the UDG and CD populations in seven galaxy clusters and tracing the evolutionary histories of 112 present-day CDs. We confirm that TNG100 reproduces the observed spatial anticorrelation, with CDs concentrated within d/R_200 ≲ 0.2 and UDGs preferentially inhabiting the cluster outskirts. Tracing CDs back in time, we identified eight systems whose progenitors undergo a transient UDG phase, with extremely high gas fractions (f_gas ≳ 0.8), immediately before cluster infall. In all eight systems, a vast majority of the present-day stellar mass was assembled after the epoch of maximum spatial extent, and the peak star formation rate during the transformation is the highest each galaxy achieves across its entire lifetime. The UDG progenitors show no prominent stellar cores before infall, demonstrating that the compact component of the resulting CD is not an exposed preexisting nucleus but is instead freshly built through starburst-driven star formation during the stripping process itself. Our results reveal a physically motivated UDG-to-CD transformation pathway driven entirely by cluster environment that is fundamentally distinct from classical tidal stripping scenarios and highlight the critical role of gas richness as a prerequisite for this channel.
ER -