The SMUGGLE-Ring project: Bar and bulge effects on nuclear disk and ring formation

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Main Authors: Kwak, SungWon, Marinacci, Federico, Steinmetz, Matthias, Minchev, Ivan, Chiappini, Cristina, Schultheis, Mathias, Kim, Woong-Tae, Vogelsberger, Mark, Sales, Laura V., Li, Hui, Baek, Seungwon
Format: Preprint
Published: 2026
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author Kwak, SungWon
Marinacci, Federico
Steinmetz, Matthias
Minchev, Ivan
Chiappini, Cristina
Schultheis, Mathias
Kim, Woong-Tae
Vogelsberger, Mark
Sales, Laura V.
Li, Hui
Baek, Seungwon
author_facet Kwak, SungWon
Marinacci, Federico
Steinmetz, Matthias
Minchev, Ivan
Chiappini, Cristina
Schultheis, Mathias
Kim, Woong-Tae
Vogelsberger, Mark
Sales, Laura V.
Li, Hui
Baek, Seungwon
contents We present the first results from the SMUGGLE-Ring project, a suite of simulations employing the SMUGGLE ISM and stellar feedback model to explore nuclear structures in Milky Way-mass galaxies. We discuss results from three simulations evolved for 5 Gyr in isolation, in which we vary the classical bulge mass, while keeping the disk and halo structures identical. Nuclear stellar disks and rings emerge exclusively in our bulge models, with more massive bulges associated with earlier formation and more extended initial gas reservoirs shortly after bar formation. After gas depletion via active star formation, the nuclear stellar disks bifurcate into pressure-supported nuclear star clusters (NSCs, $v_ϕ/σ_R < 0.7$) and rotationally supported nuclear stellar rings (NSRs, $v_ϕ/σ_R = 1.2$--1.7, radii 0.64--0.76 kpc). The bulgeless model fails to build up and sustain stable nuclear gas disks against feedback disruptions. The enclosed stellar mass of NSCs ($\sim10^{9}\Msun$) dominates over that of NSRs ($\sim10^{8}\Msun$). The star formation rates decline over time due to gas depletion (NSCs 0.1--1 $\Msun$/yr, NSRs 0.01--$0.1 \Msun$/yr). Kinematics reveal outward-shifting rotation peaks with $σ$-drops in NSRs, while a fraction of stars in NSCs exhibits radial shift after 3 Gyr. These findings support inside-out NSD formation via secular bar evolution, with NSRs tracing the star-forming outer edge of the nuclear gas disk and NSCs forming the kinematically hotter inner component. The range of nuclear stellar disk sizes (0.25--0.76 kpc) falls within the observationally inferred ranges, but the existence of larger rings would require external gas flow and/or a longer period of evolution. Future SMUGGLE-Ring extensions will incorporate varying gas fractions, tidal/merger effects, and the circumgalactic medium to further elucidate nuclear diversity and outliers.
format Preprint
id arxiv_https___arxiv_org_abs_2603_12379
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The SMUGGLE-Ring project: Bar and bulge effects on nuclear disk and ring formation
Kwak, SungWon
Marinacci, Federico
Steinmetz, Matthias
Minchev, Ivan
Chiappini, Cristina
Schultheis, Mathias
Kim, Woong-Tae
Vogelsberger, Mark
Sales, Laura V.
Li, Hui
Baek, Seungwon
Astrophysics of Galaxies
We present the first results from the SMUGGLE-Ring project, a suite of simulations employing the SMUGGLE ISM and stellar feedback model to explore nuclear structures in Milky Way-mass galaxies. We discuss results from three simulations evolved for 5 Gyr in isolation, in which we vary the classical bulge mass, while keeping the disk and halo structures identical. Nuclear stellar disks and rings emerge exclusively in our bulge models, with more massive bulges associated with earlier formation and more extended initial gas reservoirs shortly after bar formation. After gas depletion via active star formation, the nuclear stellar disks bifurcate into pressure-supported nuclear star clusters (NSCs, $v_ϕ/σ_R < 0.7$) and rotationally supported nuclear stellar rings (NSRs, $v_ϕ/σ_R = 1.2$--1.7, radii 0.64--0.76 kpc). The bulgeless model fails to build up and sustain stable nuclear gas disks against feedback disruptions. The enclosed stellar mass of NSCs ($\sim10^{9}\Msun$) dominates over that of NSRs ($\sim10^{8}\Msun$). The star formation rates decline over time due to gas depletion (NSCs 0.1--1 $\Msun$/yr, NSRs 0.01--$0.1 \Msun$/yr). Kinematics reveal outward-shifting rotation peaks with $σ$-drops in NSRs, while a fraction of stars in NSCs exhibits radial shift after 3 Gyr. These findings support inside-out NSD formation via secular bar evolution, with NSRs tracing the star-forming outer edge of the nuclear gas disk and NSCs forming the kinematically hotter inner component. The range of nuclear stellar disk sizes (0.25--0.76 kpc) falls within the observationally inferred ranges, but the existence of larger rings would require external gas flow and/or a longer period of evolution. Future SMUGGLE-Ring extensions will incorporate varying gas fractions, tidal/merger effects, and the circumgalactic medium to further elucidate nuclear diversity and outliers.
title The SMUGGLE-Ring project: Bar and bulge effects on nuclear disk and ring formation
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2603.12379