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| Main Authors: | , , |
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| Format: | Preprint |
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2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.26722 |
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| _version_ | 1866917534239817728 |
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| author | Soler-Terricabras, Toni Romero-Gómez, Mercè Roca-Fàbrega, Santi |
| author_facet | Soler-Terricabras, Toni Romero-Gómez, Mercè Roca-Fàbrega, Santi |
| contents | The main goal of this work is to quantify, through a robust methodology, the contribution of invariant manifolds to the formation of spiral arms in a pure N-body simulation, setting up a machinery to perform similar tests in other and more complex simulations. We computed the invariant manifolds associated with the hyperbolic equilibrium points of the effective potential and quantified the fraction of particles whose motion is governed by these phase-space structures. We then compared the temporal evolution of this trapped fraction with the strength of the spiral arms, traced by the A2 Fourier amplitude. We find a correlation between the fraction of trapped particles in the unstable exterior branches of the invariant manifolds and the strength of spiral arms. In particular, we determine that up to 50% of all the particles located on the spiral arms region (and up to 90% from the manifold-compatible population) are trapped by the manifolds, with oscillations of period of the order of 100 Myr. Invariant manifolds provide a dynamically relevant framework for understanding the formation of spiral structure in pure N-body simulations of barred galaxies. We present the first quantitative evidence, based on a fully self-consistent N-body model, that a significant fraction of spiral-arm particles is governed by manifold-driven dynamics. These particles act as seeds of overdensities that subsequently evolve into fully developed spiral arms through the delayed gravitational response of the disc to the self-gravity of the manifold-trapped material. The influence of the invariant manifolds remains non-negligible at all times, and phases of stronger spiral structure are associated with higher trapped fractions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_26722 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Invariant manifolds in barred galaxy simulations. II. Quantitative evidence of manifold-trapping in spiral arm formation Soler-Terricabras, Toni Romero-Gómez, Mercè Roca-Fàbrega, Santi Astrophysics of Galaxies The main goal of this work is to quantify, through a robust methodology, the contribution of invariant manifolds to the formation of spiral arms in a pure N-body simulation, setting up a machinery to perform similar tests in other and more complex simulations. We computed the invariant manifolds associated with the hyperbolic equilibrium points of the effective potential and quantified the fraction of particles whose motion is governed by these phase-space structures. We then compared the temporal evolution of this trapped fraction with the strength of the spiral arms, traced by the A2 Fourier amplitude. We find a correlation between the fraction of trapped particles in the unstable exterior branches of the invariant manifolds and the strength of spiral arms. In particular, we determine that up to 50% of all the particles located on the spiral arms region (and up to 90% from the manifold-compatible population) are trapped by the manifolds, with oscillations of period of the order of 100 Myr. Invariant manifolds provide a dynamically relevant framework for understanding the formation of spiral structure in pure N-body simulations of barred galaxies. We present the first quantitative evidence, based on a fully self-consistent N-body model, that a significant fraction of spiral-arm particles is governed by manifold-driven dynamics. These particles act as seeds of overdensities that subsequently evolve into fully developed spiral arms through the delayed gravitational response of the disc to the self-gravity of the manifold-trapped material. The influence of the invariant manifolds remains non-negligible at all times, and phases of stronger spiral structure are associated with higher trapped fractions. |
| title | Invariant manifolds in barred galaxy simulations. II. Quantitative evidence of manifold-trapping in spiral arm formation |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2605.26722 |