Quasars
Mostrando 1-12 de 24 artigos, teses e dissertações.
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1. Acreção a buracos negros supermassivos no universo presente
Há evidências contundentes de que u ma parcela significativa das galáxias no universo presente hospedam buracos negros supermassivos que acretam gás a baixas taxas. Tal acreção origina os núcleos ativos de baixa luminosidade (LLAGNs), que constituem a população dominante de AGNs nas galáxias próximas. O objetivo deste trabalho é elucidar a nature
Publicado em: 2009
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2. Estudo de variabilidades espectral e temporal de radiofontes
We present the results of a 2-year project to monitor the spectral and temporal variability of Sagittarius A, Centaurus A, OV236 and the Einsteins Ring PKS1830-211 from 2004 to 2006. The observational data were obtained from the Itapetinga Radio Telescope at 22 and 43GHz. The data at 4,8, 8,0 and 14,5GHz for OV236 and PKS1830-211 were taken from the Michigan
Publicado em: 2007
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3. MULTIFREQUENCY OBSERVATIONS OF QUASARS CSS USING THE VLBA / OBSERVAÇÕES MULTIFREQÜÊNCIA DE QUASARES CSS UTILIZANDO O VLBA
Nesta tese, discuto resultados de observações em polarização de radiofontes compactas selecionadas do grupo CSS, feitas com o Very Long Baseline Array em freqüências selecionadas nas bandas de observação em 18 cm, 21 cm, 13 cm e 6 cm. Uma análise da emissão polarizada para os quasares 3C216, 3C147, 3C119 e 3C43 permite concluir que todos mostram um
Publicado em: 2006
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4. Is it possible to test brane-world scenarios by observation of quasars and microquasars?
The aim of this work is to present a possible way to estimate observational electromagnetical clues in the spectrum of quasars and microquasars due to the presence of extra dimensions. Here we analyze two possible ways to detect these electromagnetic signals: by the brane corrected accretion mechanism and by production of electromagnetic KK modes. We show th
Brazilian Journal of Physics. Publicado em: 2005-12
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5. Relativistic jets and accretion phenomena associated with galactic and extragalactic black holes
More than a dozen binary star systems hosting stellar-mass black holes have been discovered in our galaxy. Some of them eject collimated relativistic jets with apparent velocities larger than the light speed. These objects have been named microquasars thanks to their similarity with the distant quasars or active nuclei of galaxies that host supermassive blac
Brazilian Journal of Physics. Publicado em: 2005-12
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6. Prospectivas de imageamento de sistemas DLA a partir de técnicas de síntese espectral de galáxias / Study of the spectra composed by qso s and DLA s
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 12/12/2002
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7. Exploring the global topology of the universe
We review the work done by our group on cosmic topology. It ranges from early atempts to solve a famous controversy about quasars thought the multiplicity of images, to quantum cosmology in this context and an application to QED renormalization.
Brazilian Journal of Physics. Publicado em: 2002-12
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8. Prospectivas de imageamento de sistemas DLA a partir de técnicas de síntese espectral de galáxias / Study of the spectra composed by qso s and DLA s
Hoje em dia, a formação das galáxias não está totalmente compreendida. Acredita-se que foram formadas a partir de nuvens de alta densidade de hidrogênio neutro, com diferentes graus de metalicidade. Estas nuvens acham-se em maior número em redshifts (z)altos (2 - 4.5). Devido a suas baixas luminosidades, é difícil descobrí-las, de forma isolada. Na
Publicado em: 2002
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9. Causes and effects of the first quasars.
The light we observe from the most distant known quasars set out when the Universe was about 200 times denser than it is now and less than one-tenth of its present age. The existence of these objects implies that galaxy formation had already, at that early epoch, proceeded to the stage when massive (>10(8)M[symbol, see text]) objects had accumulated in the c
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10. Possible links between BL Lacertae objects and quasars from very long baseline interferometry radio data.
Systematic differences in the very long baseline interferometry (VLBI) radio polarization structure and average VLBI component speeds of BL Lacertae objects and quasars support the view that the observational distinction between these classes, based in large part on the strength of their optical line emission, is meaningful; in other words, this distinction
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11. The x-ray luminosity-redshift relationship of quasars
Chronometric cosmology provides an excellent fit for the phenomenological x-ray luminosity-redshift relationship for 49 quasars observed by the Einstein satellite. Analysis of the data on the basis of the Friedmann cosmology leads to a correlation of absolute x-ray luminosity with redshift of >0.8, which is increased to ∼1 in the bright envelope. Although
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12. Quasars and active galactic nuclei: high resolution radio imaging.