On the Spiral Structure of Disk Galaxies

LIN, C. C.; SHU, FRANK H.

doi:10.1142/9789814415651_0033

Cited by 16 publications

(23 citation statements)

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“…This observational result is also in agreement with the theory of Lin & Shu (1964) and a general result from n-body simulations of disk galaxies, namely that spiral arms are in fact not steady-state but recurrent and multiple modes overlap each other (e.g. Fux 1999).…”

Section: Multiple Pattern Speedssupporting

confidence: 89%

Milky Way Gas Dynamics

Englmaier

Gerhard

2006

Celestial Mech Dyn Astr

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The Milky Way is made up of a central bar, a disk with embedded spiral arms, and a dark matter halo. Observational and theoretical constraints for the characteristic parameters of these components will be presented, with emphasis on the constraints from the dynamics of the Milky Way gas. In particular, the fraction of dark matter inside the solar radius, the location of the main resonances, and the evidence for multiple pattern speeds will be discussed.

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Section: Multiple Pattern Speedssupporting

confidence: 89%

Milky Way Gas Dynamics

Englmaier

Gerhard

2006

Celestial Mech Dyn Astr

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“…where g is the acceleration of gravity, which is taken as a constant; θ 0 is the potential temperature of static air, θ (0) is the zero order approximation of the potential temperature departure from θ 0 , ζ (0) is the zero order approximation of the vertical component of relative vorticity; and ∇ 2 h is the two-dimensional (horizontal) Laplacian operator. Eliminating w (1) from Eq. (1), we obtain the conversation law for the quasi-geostrophic potential vorticity…”

Section: Basic Equationsmentioning

confidence: 99%

“…Similarly, the constant phase lines of the Rossby wave tilt westwards with increasing of height, and this is called the spiral structure of the Rossby wave. The density wave theory of spiral waves for galaxy proposed by Lin et al [1] is widely appreciated by astronomers [2∼4] . Later, CHAO et al [5] and LIU and YANG [6,7] studied E-mail: liusk@pku.edu.cn the spiral structures of planetary waves and typhoons, respectively.…”

Section: Introductionmentioning

confidence: 99%

Spiral Patterns of the Rossby Wave

Shi-Kuo

Dongyan

et al. 2003

Chinese J of Geophysics

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We use quasi-geostrophic motion equations describing large-scale motion in the atmosphere to obtain the steady three-dimensional stream field and the corresponding potential temperature, vorticity and divergence fields. Among them the three-dimensional velocity field constructs a nonlinear autonomous dynamical system in the physical space. It is shown that the Rossby wave has a tilting spiral structure, which represents that the stream field is horizontal convergence at lower level and ascending motion in front of trough, but descending motion and horizontal divergence at lower level behind the trough. And these make westerlies momentum from the north and the south concentrate on the center regions of the Rossby wave. This is known ordinarily as the 'negative viscosity' phenomena. It implies that the rotation of the earth and mean current are playing an important role in forming the spiral structure of the Rossby wave.

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“…[7,8] To date, only a few papers have focused on the photoluminescence properties of rare-earth-doped Gd 2 Ti 2 O 7 powders. [7][8][9][10][11][12][13] In this paper, we present a detailed analysis of the luminescence of Dy 3+ and Tm 3+ in a Gd 2 Ti 2 O 7 nanoscaled host.…”

Section: Introductionmentioning

confidence: 99%

White‐ and blue‐light‐emitting dysprosium(III) and terbium(III)‐doped gadolinium titanate phosphors

et al. 2016

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Here we report the synthesis and structural, morphological, and photoluminescence analysis of white- and blue-light-emitting Dy - and Tm -doped Gd Ti O nanophosphors. Single-phase cubic Gd Ti O nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy -doped and ~50 nm for Tm -doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy -doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue-light excitation. Intense blue light was obtained for Tm -doped Gd Ti O under UV excitation suggesting that this material could be used as a blue phosphor.

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On the Spiral Structure of Disk Galaxies

Cited by 16 publications

References 0 publications

Milky Way Gas Dynamics

Milky Way Gas Dynamics

Spiral Patterns of the Rossby Wave

White‐ and blue‐light‐emitting dysprosium(III) and terbium(III)‐doped gadolinium titanate phosphors

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