EDGE:  a new model for nuclear star cluster formation in dwarf galaxies

Emily I Gray; Justin I Read; Ethan Taylor; Matthew D A Orkney; Martin P Rey; Robert M Yates; Stacy Y Kim; Noelia E D Noël; Oscar Agertz; Eric P Andersson; Andrew Pontzen

doi:10.1093/mnras/staf521

EDGE: a new model for nuclear star cluster formation in dwarf galaxies

Emily I Gray, Justin I Read, Ethan Taylor, Matthew D A Orkney, Martin P Rey, Robert M Yates, Stacy Y Kim, Noelia E D Noël, Oscar Agertz, Eric P Andersson, Andrew Pontzen

Research output: Contribution to journal › Article › peer-review

Abstract

Nuclear star clusters (NSCs) are among the densest stellar systems in the Universe and are found at the centres of many spiral and elliptical galaxies, and up to 40 percent of dwarf galaxies. However, their formation mechanisms, and possible links to globular clusters (GCs), remain debated. This paper uses cosmological simulations of dwarf galaxies at a spatial resolution of pc to present a new formation mechanism for NSCs, showing they naturally emerge in a subset dwarfs with present-day halo masses of. The mechanism proceeds following reionization quenching that stops the supply of cold star-forming gas. Next, a major merger causes a central dense gas reservoir to form, eventually exciting rapid cooling, leading to a significant starburst. An NSC forms in this starburst that quenches star formation thereafter. The result is a nucleated dwarf that has two stellar populations with distinct age: pre-and post-reionization. Our mechanism is unique because of the low mass of the host dwarf, and because it naturally leads to NSCs that contain two stellar populations with a 1 billion year age separation. The former means that NSCs, formed in this way, can accrete on to galaxies of almost all masses. If these accreted NSCs fall to the centre of their host galaxy, they could then seed the formation of NSCs everywhere. The latter yields a predicted colour-magnitude diagram that has two distinct main sequence turn-offs. Several GCs orbiting the Milky Way, including Omega Centauri and M54, show similar behaviour, suggesting that they may be accreted NSCs.

Original language	English
Pages (from-to)	1167-1179
Number of pages	13
Journal	Monthly Notices of the Royal Astronomical Society
Volume	539
Issue number	2
DOIs	https://doi.org/10.1093/mnras/staf521
Publication status	Published - 1 May 2025

Data Availability Statement

Data available upon reasonable request.

Acknowledgements

We would like to thank the anonymous referee for a constructive review that improved the quality of the manuscript. The authors would like to thank Dr Santi Cassisi and Dr Alex Riley for their support with synthetic CMD tools, as well as Madeleine McKenzie and Oliver Camilleri for the useful feedback and interesting discussions.

This work also used the DiRAC@Durham (cosma6) facility managed by the Institute for Computational Cosmology on behalf of the STFC DiRAC HPC Facility (www.dirac.ac.uk). The equipment was funded by BEIS capital funding via STFC capital grants ST/P002293/1, ST/R002371/1, and ST/S002502/1, Durham University, and STFC operations grant ST/R000832/1. DiRAC is part of the National e-Infrastructure.

Funding

This project has received funding from the European Union\u2019s Horizon 2020 research and innovation programme under grant agreement No. 818085 GMGalaxies. JIR would like to thank the STFC for support from grants ST/Y002865/1 and ST/Y002857/1. ET acknowledges the UKRI Science and Technology Facilities Council (STFC) for support (grant ST/V50712X/1). MO acknowledges funding from the European Research Council (ERC) under the European Union\u2019s Horizon 2020 research and innovation programme (grant agreement No. 852839). MR is supported by the Beecroft Fellowship funded by Adrian Beecroft. OA acknowledges support from the Knut and Alice Wallenberg Foundation, the Swedish Research Council (grant 2019-04659), and the Swedish National Space Agency (SNSA Dnr 2023-00164). This work also used the DiRAC@Durham (cosma6) facility managed by the Institute for Computational Cosmology on behalf of the STFC DiRAC HPC Facility ( www.dirac.ac.uk ). The equipment was funded by BEIS capital funding via STFC capital grants ST/P002293/1, ST/R002371/1, and ST/S002502/1, Durham University, and STFC operations grant ST/R000832/1. DiRAC is part of the National e-Infrastructure. We w ould lik e to thank the anonymous referee for a constructive re vie w that impro v ed the quality of the manuscript. The authors w ould lik e to thank Dr Santi Cassisi and Dr Ale x Rile y for their sup-port with synthetic CMD tools, as well as Madeleine McKenzie and Oliver Camilleri for the useful feedback and interesting discussions. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 818085 GMGalaxies. JIR would like to thank the STFC for support from grants ST/Y002865/1 and ST/Y002857/1. ET acknowledges the UKRI Science and Technology Facilities Council (STFC) for support (grant ST/V50712X/1). MO acknowledges fund-ing from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 852839). MR is supported by the Beecroft Fellowship funded by Adrian Beecroft. OA acknowledges support from the Knut and Alice Wallenberg Foundation, the Swedish Research Council (grant 2019-04659), and the Swedish National Space Agency (SNSA Dnr 2023-00164). This work also used the DiRAC@Durham (cosma6) facility managed by the Institute for Computational Cosmology on be-half of the STFC DiRAC HPC Facility ( www.dirac.ac.uk). The equipment was funded by BEIS capital funding via STFC capital grants ST/P002293/1, ST/R002371/1, and ST/S002502/1, Durham University, and STFC operations grant ST/R000832/1. DiRAC is part of the National e-Infrastructure

Funders	Funder number
Horizon 2020 Framework Programme	818085 GMGalaxies
European Research Council	852839
Vetenskapsrådet	2019-04659
Swedish National Space Agency	Dnr 2023-00164
Science and Technology Facilities Council	ST/Y002857/1, ST/R002371/1, ST/S002502/1, ST/P002293/1, ST/Y002865/1, ST/V50712X/1
Durham University	ST/R000832/1

Keywords

dark matter
galaxies: dwarf
galaxies: evolution
galaxies: haloes
galaxies: star clusters: general
methods: numerical

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1093/mnras/staf521Licence: CC BY

Cite this

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title = "EDGE: a new model for nuclear star cluster formation in dwarf galaxies",

abstract = "Nuclear star clusters (NSCs) are among the densest stellar systems in the Universe and are found at the centres of many spiral and elliptical galaxies, and up to 40 percent of dwarf galaxies. However, their formation mechanisms, and possible links to globular clusters (GCs), remain debated. This paper uses cosmological simulations of dwarf galaxies at a spatial resolution of pc to present a new formation mechanism for NSCs, showing they naturally emerge in a subset dwarfs with present-day halo masses of. The mechanism proceeds following reionization quenching that stops the supply of cold star-forming gas. Next, a major merger causes a central dense gas reservoir to form, eventually exciting rapid cooling, leading to a significant starburst. An NSC forms in this starburst that quenches star formation thereafter. The result is a nucleated dwarf that has two stellar populations with distinct age: pre-and post-reionization. Our mechanism is unique because of the low mass of the host dwarf, and because it naturally leads to NSCs that contain two stellar populations with a 1 billion year age separation. The former means that NSCs, formed in this way, can accrete on to galaxies of almost all masses. If these accreted NSCs fall to the centre of their host galaxy, they could then seed the formation of NSCs everywhere. The latter yields a predicted colour-magnitude diagram that has two distinct main sequence turn-offs. Several GCs orbiting the Milky Way, including Omega Centauri and M54, show similar behaviour, suggesting that they may be accreted NSCs.",

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author = "Gray, {Emily I} and Read, {Justin I} and Ethan Taylor and Orkney, {Matthew D A} and Rey, {Martin P} and Yates, {Robert M} and Kim, {Stacy Y} and No{\"e}l, {Noelia E D} and Oscar Agertz and Andersson, {Eric P} and Andrew Pontzen",

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AU - Gray, Emily I

AU - Read, Justin I

AU - Taylor, Ethan

AU - Orkney, Matthew D A

AU - Rey, Martin P

AU - Yates, Robert M

AU - Kim, Stacy Y

AU - Noël, Noelia E D

AU - Agertz, Oscar

AU - Andersson, Eric P

AU - Pontzen, Andrew

PY - 2025/5/1

Y1 - 2025/5/1

N2 - Nuclear star clusters (NSCs) are among the densest stellar systems in the Universe and are found at the centres of many spiral and elliptical galaxies, and up to 40 percent of dwarf galaxies. However, their formation mechanisms, and possible links to globular clusters (GCs), remain debated. This paper uses cosmological simulations of dwarf galaxies at a spatial resolution of pc to present a new formation mechanism for NSCs, showing they naturally emerge in a subset dwarfs with present-day halo masses of. The mechanism proceeds following reionization quenching that stops the supply of cold star-forming gas. Next, a major merger causes a central dense gas reservoir to form, eventually exciting rapid cooling, leading to a significant starburst. An NSC forms in this starburst that quenches star formation thereafter. The result is a nucleated dwarf that has two stellar populations with distinct age: pre-and post-reionization. Our mechanism is unique because of the low mass of the host dwarf, and because it naturally leads to NSCs that contain two stellar populations with a 1 billion year age separation. The former means that NSCs, formed in this way, can accrete on to galaxies of almost all masses. If these accreted NSCs fall to the centre of their host galaxy, they could then seed the formation of NSCs everywhere. The latter yields a predicted colour-magnitude diagram that has two distinct main sequence turn-offs. Several GCs orbiting the Milky Way, including Omega Centauri and M54, show similar behaviour, suggesting that they may be accreted NSCs.

AB - Nuclear star clusters (NSCs) are among the densest stellar systems in the Universe and are found at the centres of many spiral and elliptical galaxies, and up to 40 percent of dwarf galaxies. However, their formation mechanisms, and possible links to globular clusters (GCs), remain debated. This paper uses cosmological simulations of dwarf galaxies at a spatial resolution of pc to present a new formation mechanism for NSCs, showing they naturally emerge in a subset dwarfs with present-day halo masses of. The mechanism proceeds following reionization quenching that stops the supply of cold star-forming gas. Next, a major merger causes a central dense gas reservoir to form, eventually exciting rapid cooling, leading to a significant starburst. An NSC forms in this starburst that quenches star formation thereafter. The result is a nucleated dwarf that has two stellar populations with distinct age: pre-and post-reionization. Our mechanism is unique because of the low mass of the host dwarf, and because it naturally leads to NSCs that contain two stellar populations with a 1 billion year age separation. The former means that NSCs, formed in this way, can accrete on to galaxies of almost all masses. If these accreted NSCs fall to the centre of their host galaxy, they could then seed the formation of NSCs everywhere. The latter yields a predicted colour-magnitude diagram that has two distinct main sequence turn-offs. Several GCs orbiting the Milky Way, including Omega Centauri and M54, show similar behaviour, suggesting that they may be accreted NSCs.

KW - dark matter

KW - galaxies: dwarf

KW - galaxies: evolution

KW - galaxies: haloes

KW - galaxies: star clusters: general

KW - methods: numerical

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DO - 10.1093/mnras/staf521

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JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

EDGE: a new model for nuclear star cluster formation in dwarf galaxies

Abstract

Data Availability Statement

Acknowledgements

Funding

Keywords

ASJC Scopus subject areas

Access to Document

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Engineering Dwarf Galaxy at the Edge of galaxy formation

Cite this

EDGE: a new model for nuclear star cluster formation in dwarf galaxies

Abstract

Data Availability Statement

Acknowledgements

Funding

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Projects

Engineering Dwarf Galaxy at the Edge of galaxy formation

Cite this