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Spiral Structure as a Recurrent Instability
Sellwood, J. A.
A long-standing controversy in studies of spiral structure has concerned the lifetimes of individual spiral patterns. Much theoretical work has sought quasi-stationary spiral modes while N-body simulations have consistently displayed recurrent, short-lived patterns. The simulations manifest a recurrent cycle of true instabilities related to small-…
Local Kinematics of Classical Cepheids
Zhu, Zi
Combining Hipparcos proper motions and the radial velocity data, we have studied the Cepheid kinematics on the basis of the three-dimensional Ogorodnikov-Milne model. The results seem to show a slight contracting motion of the Galaxy in the solar neighbourhood, ∂ Vθ / ∂θ / R = ‑2.60 ± 1.07 km s-1 kpc-1, which is al…
The Velocity Field of Young Stars in the Solar Neighbourhood
Comerón, F.; Figueras, F.; Torra, J. +1 more
A sample of O- and B-type stars with Hipparcos astrometric data, ages computed from Strömgren photometry and radial velocities, has been used to characterize the structure, age and kinematics of the Gould Belt system. The local spiral structure of our galaxy is determined from this sample, and also from a sample of Hipparcos Cepheid stars. The Gou…
Separation between Gould Belt and Disk Stars in the Solar Neighbourhood
Alfaro, E. J.; Cabrera-Caño, J.; Elias, F.
The adoption of a parametric model for the spatial distribution of Gould Belt and Galactic Disk stars allows the classification by their membership probabilities of stars from the Hipparcos catalogue in the Solar vicinity and the estimation of structural parameters for both stellar systems for several age groups. The observed kinematics of Gould B…