The NIVARIA-Local Group simulations: Unveiling the origin of rotation curve diversity in dwarf galaxies and its connection to galaxy morphology

A. Contreras-Santos; A. Di Cintio; A. Negri; J. Sarrato-Alós; S. Cardona-Barrero; G. García-Bethencourt; C. Brook; N. I. Libeskind; A. Knebe; A. Macciò

arXiv · 2610.15071

The NIVARIA-Local Group simulations: Unveiling the origin of rotation curve diversity in dwarf galaxies and its connection to galaxy morphology

A. Contreras-Santos·A. Di Cintio·A. Negri·J. Sarrato-Alós·S. Cardona-Barrero·G. García-Bethencourt·C. Brook·N. I. Libeskind·A. Knebe·A. Macciò

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Abstract

Dwarf galaxies exhibit a large diversity in rotation curve shapes, challenging galaxy formation models within the $Λ$CDM paradigm. We present NIVARIA-LG, a new suite of cosmological simulations studying dwarf galaxy evolution in realistic Local Group environments. This intermediate-resolution pilot lays the groundwork for the full-scale NIVARIA project. The simulations combine constrained Local Group initial conditions from HESTIA with the NIHAO galaxy formation model. The simulated galaxies reproduce observed stellar-to-halo mass relations, match the Baryonic Tully-Fisher relation, and capture the distribution of stellar effective radii, including compact and diffuse galaxies. We analyse the structural and kinematic properties of isolated dwarf galaxies with $10^7 \lesssim M_\star/M_\odot \lesssim 10^{10}$, focusing on rotation curve diversity. NIVARIA-LG naturally produces a broad range of rotation curve shapes, including slowly rising systems underrepresented in previous simulations and steep rotation curves. We find that rotation curve diversity is primarily associated with gas extent and inner dark matter structure: more extended gas and shallower inner density profiles correspond to more slowly rising curves, while stellar effective radius shows little independent association. Individual galaxies show that rotation curve shapes change rapidly as gas is redistributed during assembly. Recent accretion events are also associated with more slowly rising curves in the most massive dwarfs. Together, these results suggest that rotation curve diversity is linked to the baryonic cycle, which shapes the inner dark matter distribution. The Local Group environment and its filaments influence this evolution by regulating gas accretion and redistribution, producing the observed diversity in rotation curve shapes.

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A. Contreras-Santos, A. Di Cintio, A. Negri, J. Sarrato-Alós, S. Cardona-Barrero, G. García-Bethencourt, C. Brook, N. I. Libeskind, A. Knebe, A. Macciò. 2026-10-10. The NIVARIA-Local Group simulations: Unveiling the origin of rotation curve diversity in dwarf galaxies and its connection to galaxy morphology. https://arxiv.org/abs/2610.15071

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