Galaxies Spiral
Mostrando 1-12 de 12 artigos, teses e dissertações.
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1. Fotometria, decomposição e correlações para galáxias espirais próximas do projeto GHASP / Photometry, decomposition and correlations for nearby spiral galaxies from the GHASP survey
The spiral galaxies still challenge the theories that try to explain how the universe has turned into what we see today. In particular, in the context of the hierarchical structure formation, it is difficult to understand how galaxies can be so similar, obeying such strict scaling relations, in spite of their distinct evolutionary histories. In order to clar
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 24/10/2011
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2. Correção logarítmica no potencial Newtoniano e sua aplicação a galáxias espirais
A well elaborated characterization of the masses of the galaxies is of basic importance to understand the formation and the evolution of the galaxies, as well as the Universe. The circular speed of the spiral galaxies is used to estimate the mass of the galaxies. The observacional data of the rotation curves exactly show that the circular speeds practically
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 03/08/2007
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3. Triaxial halos and the axis ratio of spiral galaxies / "Halos triaxiais e a razão axial de galáxias espirais"
A triaxialidade dos halos das galáxias espirais foi estudada através das funções de distribuição de razões axiais aparentes dos seus discos. Utilizou-se uma amostra de galáxias limitada por magnitude (g<16). Foram selecionadas ~1600 galáxias espirais do SDSS (Sloan Digital Sky Survey), que foram classificadas morfologicamente por inspeção visual.
Publicado em: 2006
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4. Color Gradients and the Secular Evolutionary Scenario in Late-Type Spiral Galaxies / Gradientes de Cor e o Cenário de Evolução Secular em Galáxias Espirais de Tipo Tardio
Nós realizamos um estudo estatístico do comportamento de perfis de cor em bandas largas (UBV) para 257 galáxias espirais do tipo Sbc, ordinárias e barradas, utilizando dados obtidos através de fotometria fotoelétrica de abertura, disponíveis na literatura (Longo &de Vaucouleurs 1983,1985). Nós determinamos os gradientes de cor (B-V) e (U-B) para as g
Publicado em: 1999
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5. On the dynamical basis of the classification of normal galaxies
Some realistic galaxy models have been found to support discrete unstable spiral modes. Here, through the study of the relevant physical mechanisms and an extensive numerical investigation of the properties of the dominant modes in a wide class of galactic equilibria, we show how spiral structures are excited with different morphological features, depending
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6. Discrete spiral modes in disk galaxies: Some numerical examples based on density wave theory
Discrete growing spiral modes are calculated, on the basis of principles of stellar dynamics, according to the recently developed asymptotic theory of density waves for spiral structure in galaxies. From the growth rates obtained, it appears likely that several spiral modes coexist in a given disk galaxy. General properties of these modes are described for t
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7. Unstable spiral modes in disk-shaped galaxies: A general fluid dynamical theory with some preliminary results*
A numerical scheme has been devised to calculate discrete spiral modes in a fluid-dynamical model of disk galaxies. The procedure is free from the usual restrictions imposed upon the asymptotic theory. A radiation condition has been formulated as one of the boundary conditions. For a test model galaxy with moderately low surface density, quantitative agreeme
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8. Unstable spiral modes in disk-shaped galaxies: Enhancement of growth rate*
An additional effect not considered in our earlier papers is found to enhance the rate of growth of spiral modes in disk-shaped galaxies. This enhanced growth appears to be attributable to the combined influence of differential rotation and tangential forces. For certain galaxy models, rapid temporal growths are possible (comparable to those found in numeric
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9. ON THE SPIRAL STRUCTURE OF DISK GALAXIES, II. OUTLINE OF A THEORY OF DENSITY WAVES*
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10. Unstable spiral modes in disk-shaped galaxies
The mechanisms for the maintenance and the excitation of trailing spiral modes of density waves in diskshaped galaxies, as proposed by Lin in 1969 and by Mark recently, are substantiated by an analysis of the gas-dynamical model of the galaxy. The self-excitation of the unstable mode in caused by waves propagating outwards from the corotation circle, which c
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11. Galaxy dynamics and the mass density of the universe.
Dynamical evidence accumulated over the past 20 years has convinced astronomers that luminous matter in a spiral galaxy constitutes no more than 10% of the mass of a galaxy. An additional 90% is inferred by its gravitational effect on luminous material. Here I review recent observations concerning the distribution of luminous and nonluminous matter in the Mi
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12. The nuclear region of the spiral galaxy M81.
Very-long-baseline radio interferometry images of the nuclear region of the nearby spiral galaxy M81 reveal the most compact galactic core outside the Galaxy of which the size has been determined: 700 x 300 astronomical units (AU). The observations exclude a starburst or supernova interpretation for the core. Instead they favor an active galactic nucleus. Th