LYRA: The formation and growth of nuclear star clusters in dwarf galaxies
Abstract
Nuclear star clusters (NSCs) are dense massive star clusters ubiquitous in galactic centres across various mass regimes, present in up to ∼30 per cent of dwarf galaxies with M⋆<107 M⊙. Although their main growth pathways are well studied, there is still ongoing debate regarding their formation. We use the LYRA cosmological hydrodynamical simulations to study the formation and growth of NSCs in a sample of six dwarf galaxies, where we identify NSCs with masses MNSC ∼ 104 − 106 M⊙ in all galaxies in our sample. The NSCs in our sample emerge at early times as a compact component, with the host galaxy growing around them. This is consistent with a scenario in which NSCs are among the earliest structures to form in a galaxy. We characterise the origin of the stars that constitute the NSCs and explore the properties of the stellar populations in each of these channels. We find that most of the NSC mass originates from in-situ star formation within the NSCs themselves. While this might appear at odds with current observations, the bulk of this star formation occurs at early times, resulting in a significant population of old and metal-poor stars, in agreement with an early NSC formation. We also identify galaxy-galaxy mergers as a significant contributor to the NSC mass, with usually one merger dominating this contribution. Our results highlight the complexity in the growth history of NSCs in dwarf galaxies and highlight the importance of considering additional growth channels for NSCs in dwarfs galaxies.
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BibTeX
@misc{sureda2026lyra,
title = {{LYRA: The formation and growth of nuclear star clusters in dwarf galaxies}},
author = {Joaquin Sureda and Azadeh Fattahi and Sownak Bose and Mariya Lyubenova and Jessica E. Doppel and Thales Gutcke and Katja Fahrion and Rüdiger Pakmor},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.38179},
eprint = {2609.38179},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.38179},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - LYRA: The formation and growth of nuclear star clusters in dwarf galaxies
AU - Joaquin Sureda
AU - Azadeh Fattahi
AU - Sownak Bose
AU - Mariya Lyubenova
AU - Jessica E. Doppel
AU - Thales Gutcke
AU - Katja Fahrion
AU - Rüdiger Pakmor
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.38179
UR - https://arxiv.org/abs/2609.38179
AB - Nuclear star clusters (NSCs) are dense massive star clusters ubiquitous in galactic centres across various mass regimes, present in up to ∼30 per cent of dwarf galaxies with M_⋆<10^7 M_⊙. Although their main growth pathways are well studied, there is still ongoing debate regarding their formation. We use the LYRA cosmological hydrodynamical simulations to study the formation and growth of NSCs in a sample of six dwarf galaxies, where we identify NSCs with masses M_NSC ∼ 10^4 − 10^6 M_⊙ in all galaxies in our sample. The NSCs in our sample emerge at early times as a compact component, with the host galaxy growing around them. This is consistent with a scenario in which NSCs are among the earliest structures to form in a galaxy. We characterise the origin of the stars that constitute the NSCs and explore the properties of the stellar populations in each of these channels. We find that most of the NSC mass originates from in-situ star formation within the NSCs themselves. While this might appear at odds with current observations, the bulk of this star formation occurs at early times, resulting in a significant population of old and metal-poor stars, in agreement with an early NSC formation. We also identify galaxy-galaxy mergers as a significant contributor to the NSC mass, with usually one merger dominating this contribution. Our results highlight the complexity in the growth history of NSCs in dwarf galaxies and highlight the importance of considering additional growth channels for NSCs in dwarfs galaxies.
ER -