Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar?
Galactic bars can form via the internal bar instability or external tidal perturbations by other galaxies. We systematically compare the properties of the bars formed through the two mechanisms with a series of controlled N -body simulations that form bars through internal or external mechanisms. We...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad9bae |
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| author | Yirui Zheng Juntai Shen |
| author_facet | Yirui Zheng Juntai Shen |
| author_sort | Yirui Zheng |
| collection | DOAJ |
| description | Galactic bars can form via the internal bar instability or external tidal perturbations by other galaxies. We systematically compare the properties of the bars formed through the two mechanisms with a series of controlled N -body simulations that form bars through internal or external mechanisms. We create three disk galaxy models with different dynamical “hotness” and evolve them in isolation and under flyby interactions. In the cold- and warm-disk models, where bars can form spontaneously in isolation, tidally induced bars are promoted to a more “advanced” evolutionary stage. However, these bars have similar pattern speeds to those formed spontaneously within the same disk. Bars formed from both mechanisms have similar distributions in pattern-speed–bar-strength (Ω _p − A _2 ) space and exhibit comparable ratios of corotation radius to bar length ( ${ \mathcal R }={R}_{{\rm{CR}}}/{R}_{{\rm{bar}}}$ ). Dynamical analyses suggest that the inner stellar disk loses the same amount of angular momentum, irrespective of the presence or intensity of the perturbation, which possibly explains the resemblance between tidally and spontaneously formed bars. In the hot-disk model, which avoids the internal bar instability in isolation, a bar forms only under perturbations and rotates more slowly than those in the cold and warm disks. Thus, if “tidally induced bars” refer exclusively to those in galaxies that are otherwise stable against bar instability, they indeed rotate slower than internally induced ones. However, the pattern speed difference is due to the difference in the internal properties of the bar host galaxies, not the different formation mechanisms. |
| format | Article |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-6cdf45a62ee2432abdd8e52125df1b3f2025-01-17T08:30:02ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0197916010.3847/1538-4357/ad9baeComparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar?Yirui Zheng0https://orcid.org/0000-0001-7707-5930Juntai Shen1https://orcid.org/0000-0001-5604-1643Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, People’s Republic China ; jtshen@sjtu.edu.cn; Key Laboratory for Particle Astrophysics and Cosmology (MOE) / Shanghai Key Laboratory for Particle Physics and Cosmology , Shanghai 200240, People’s Republic ChinaDepartment of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, People’s Republic China ; jtshen@sjtu.edu.cn; Key Laboratory for Particle Astrophysics and Cosmology (MOE) / Shanghai Key Laboratory for Particle Physics and Cosmology , Shanghai 200240, People’s Republic ChinaGalactic bars can form via the internal bar instability or external tidal perturbations by other galaxies. We systematically compare the properties of the bars formed through the two mechanisms with a series of controlled N -body simulations that form bars through internal or external mechanisms. We create three disk galaxy models with different dynamical “hotness” and evolve them in isolation and under flyby interactions. In the cold- and warm-disk models, where bars can form spontaneously in isolation, tidally induced bars are promoted to a more “advanced” evolutionary stage. However, these bars have similar pattern speeds to those formed spontaneously within the same disk. Bars formed from both mechanisms have similar distributions in pattern-speed–bar-strength (Ω _p − A _2 ) space and exhibit comparable ratios of corotation radius to bar length ( ${ \mathcal R }={R}_{{\rm{CR}}}/{R}_{{\rm{bar}}}$ ). Dynamical analyses suggest that the inner stellar disk loses the same amount of angular momentum, irrespective of the presence or intensity of the perturbation, which possibly explains the resemblance between tidally and spontaneously formed bars. In the hot-disk model, which avoids the internal bar instability in isolation, a bar forms only under perturbations and rotates more slowly than those in the cold and warm disks. Thus, if “tidally induced bars” refer exclusively to those in galaxies that are otherwise stable against bar instability, they indeed rotate slower than internally induced ones. However, the pattern speed difference is due to the difference in the internal properties of the bar host galaxies, not the different formation mechanisms.https://doi.org/10.3847/1538-4357/ad9baeGalaxy dynamicsGalaxy kinematicsGalaxy structureBarred spiral galaxiesGalaxy bars |
| spellingShingle | Yirui Zheng Juntai Shen Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar? The Astrophysical Journal Galaxy dynamics Galaxy kinematics Galaxy structure Barred spiral galaxies Galaxy bars |
| title | Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar? |
| title_full | Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar? |
| title_fullStr | Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar? |
| title_full_unstemmed | Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar? |
| title_short | Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar? |
| title_sort | comparison of bar formation mechanisms i does a tidally induced bar rotate slower than an internally induced bar |
| topic | Galaxy dynamics Galaxy kinematics Galaxy structure Barred spiral galaxies Galaxy bars |
| url | https://doi.org/10.3847/1538-4357/ad9bae |
| work_keys_str_mv | AT yiruizheng comparisonofbarformationmechanismsidoesatidallyinducedbarrotateslowerthananinternallyinducedbar AT juntaishen comparisonofbarformationmechanismsidoesatidallyinducedbarrotateslowerthananinternallyinducedbar |