Precessing ellipses as the building blocks of spiral arms

Harsoula, M.; Zouloumi, K.; Efthymiopoulos, Christos; Contopoulos, G.

doi:10.1051/0004-6361/202140984

Cited by 6 publications

(4 citation statements)

References 58 publications

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“…In those galaxies, one found a statistical separation around 370 pc between the P arm and the D arm. Recent theoretical reviews were done by Sellwood & Masters (2022) on self-excited instabilities for a recurrent cycle of groove modes, and Harsoula et al (2021) on precessing ellipses to build arms.…”

Section: Density Waves Predicting An Age Gradientmentioning

confidence: 99%

The observed age gradient in the Milky Way—as a test for theories of spiral arm structure

Vallée

2022

Astrophys Space Sci

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Some important predictions from 4 main models of spiral arm formation are tested here, using observational data acquired for the Milky Way galaxy. Many spiral arm models (density wave, tidal wave, nuclear Lyapunov tube, or dynamic transient wave) have some consistencies with some of the observations, and some inconsistencies.Our 4 tests consist of the relative locations and relative speeds of different arm tracers away from the dust lane, and the global arm pitch angle as obtained over two Galactic quadrants and several Galactic radii, as well as the arm’s continuity of shape from Galactic quadrant IV to Galactic quadrant I.In the Milky Way, an age gradient is observed from different arm tracers, amounting to $12.9 \pm 1.1$ 12.9 ± 1.1 Myrs/kpc, or a relative speed from the dust lane of $76 \pm 10$ 76 ± 10 km/s. The presence of an age gradient is predicted by the density waves, but is not consistent with the predictions of the tidal waves, of the nuclear Lyapunov tubes, nor of the dynamic transient recurrent waves.

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Section: Density Waves Predicting An Age Gradientmentioning

confidence: 99%

The observed age gradient in the Milky Way—as a test for theories of spiral arm structure

Vallée

2022

Astrophys Space Sci

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“…We find the main families of stable and unstable periodic orbits by the Hamiltonian H 1 norm of Eq. ( 29) using the method described in Harsoula et al (2021). The main family of stable periodic orbits that has the form of precessing ellipses and supports the spiral density wave is named the x 1 orbit after Contopoulos (1975), who introduced the nomenclature of the families of periodic orbits in a spiral galaxy.…”

Section: Normal Form Constructionmentioning

confidence: 99%

“…(see Fig. 1 and corresponding text of Harsoula et al (2021) for a detailed explanation of the role of the F-strength value).…”

Section: The Modelmentioning

confidence: 99%

“…Many papers have studied these periodic orbits, in models of grand design galaxies. It has been shown that these orbits can collaborate so that the imposed model matches with the response model of spiral arms (see Contopoulos (1970Contopoulos ( , 1971Contopoulos ( , 1975, Berman (1977), Monet and Vandervoort (1978), Contopoulos and Grosbøl (1986), Patsis et al (1991), and Harsoula et al (2021)).…”

Section: Introductionmentioning

confidence: 98%

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Perturbed precessing ellipses as the building blocks of spiral arms in a barred galaxy with two pattern speeds

Harsoula

Efthymiopoulos

Contopoulos

et al. 2022

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Observations and simulations of barred spiral galaxies have shown that, in general, the spiral arms rotate at a different pattern speed to that of the bar. The main conclusion from the bibliography is that the bar rotates faster than the spiral arms with a double or even a triple value of angular velocity. The theory that prevails in explaining the formation of the spiral arms in the case of a barred spiral galaxy with two pattern speeds is the manifold theory, where the orbits that support the spiral density wave are chaotic, and are related to the manifolds emanating from the Lagrangian points L 1 and L 2 at the end of the bar. In the present study, we consider an alternative scenario in the case where the bar rotates fast enough in comparison with the spiral arms and the bar potential can be considered as a perturbation of the spiral potential. In this case, the stable elliptical orbits that support the spiral density wave (in the case of grand design galaxies) are transformed into quasiperiodic orbits (or 2D tori) with a certain thickness. The superposition of these perturbed preccesing ellipses for all the energy levels of the Hamiltonian creates a slightly perturbed symmetrical spiral density wave.

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Nonlinear Phenomena Shaping the Structure of Spiral Galaxies

Patsis

2023

Springer Proceedings in Complexity

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Precessing ellipses as the building blocks of spiral arms

Cited by 6 publications

References 58 publications

The observed age gradient in the Milky Way—as a test for theories of spiral arm structure

The observed age gradient in the Milky Way—as a test for theories of spiral arm structure

Perturbed precessing ellipses as the building blocks of spiral arms in a barred galaxy with two pattern speeds

Nonlinear Phenomena Shaping the Structure of Spiral Galaxies

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