Navegação Ciências Exatas e da Terra por Autor "Wilson, Andrew S."
Resultados 1-18 de 18
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An atlas of H II regions in nearby Seyfert galaxies
(1996) [Artigo de periódico]Continuum-subtracted Hα images of 17 nearby Seyfert galaxies are presented. The images are calibrated astrometrically usmg the Hubble Space Telescope Guide Star Catalog reference frame. For each galaxy, an inventory of HII ... -
Circumnuclear star formation in active galaxies
(1996) [Artigo de periódico]We study the gas kinematics and chemical abundances in the inner regions of six galaxies with active galactic nuclei. The galaxies were selected for having star-forming regions in rings or spirals within a few kiloparsecs ... -
Double-peaked broad line emission from the LINER nucleus of NGC 1097
(1993) [Artigo de periódico]We report the recent appearance of a very broad component in the Hα and Hβ emission lines of the weakly active nucleus of the Sersic-Pastoriza galaxy NGC 1097. Subtraction of the contribution of the stellar population from ... -
Evidence for a precessing accretion disk in the nucleus of NGC 1097
(1997) [Artigo de periódico]We present new spectroscopic observations of the LINER (and now Seyfert 1) nucleus of NGC 1097, and discuss the evolution of its broad, double-peaked Balmer lines. When originally discovered in 1991, the red peak of the ... -
Evidence of a starburst within 9 parsecs of the active nucleus of NGC 1097
(2005) [Artigo de periódico]We report evidence of a recent burst of star formation located within 9 pc of the active nucleus of NGC 1097. The observational signatures of the starburst include UV absorption lines and continuum emission from young stars ... -
Evolution of the nuclear accretion disk emission in NGC 1097 : getting closer to the black hole
(2003) [Artigo de periódico]We study the evolution of the broad, double-peaked H emission-line profile of the LINER/Seyfert 1 nucleus of NGC 1097, using 24 spectra obtained over a time span of 11 years—from 1991 November through 2002 October. While ... -
Excitation and temperature of extended gas in active galaxies. II Photoionization models with matter-bounded clouds
(1996) [Artigo de periódico]Recent reliable measurements of the weak lines of [O III]λ4363, He IIλ4686 and [Ne V]λ3426 seen in emission in extended and nuclear regions of AGN (Storchi-Bergmann et al. 1996) are used to discriminate between different ... -
Excitation and temperature of extended gas in active galaxies. I Observations
(1996) [Artigo de periódico]We have obtained long-slit spectroscopy of five active galaxies showing extended high excitation emission lines reaching distances of several kiloparsecs from the nuclei. Measurement of the fluxes of weak lines, such as ... -
Extended gas in Seyfert galaxies : near-infrared observations of 15 active nuclei
(2000) [Artigo de periódico]Results from an analysis of low-resolution …(R ~ 250)† near-infrared long-slit spectra covering simultaneously the I, J, H and K bands, for a sample of 15 Seyfert galaxies and the NGC5253 starburst nucleus, are presented. ... -
Extended gas in Seyfert galaxies: near-infrared observations of NGC 2110 and Circinus
(1999) [Artigo de periódico]We present results of near-IR long-slit spectroscopy in the J and K bands of the Seyfert 2 galaxies NGC2110 and Circinus. Our goal is to investigate the gaseous distribution, excitation, reddening and kinematics, looking ... -
Hubble Space Telescope imaging of the circinus galaxy
(2000) [Artigo de periódico]We present a Hubble Space Telescope imaging study of the nearby (4 Mpc distant) Circinus galaxy, which contains the nearest type 2 Seyfert nucleus and prominent circumnuclear star formation. Images have been obtained in ... -
Infrared emission in Seyfert 2 galaxies : reprocessed radiation from a dusty torus?
(1992) [Artigo de periódico]The nature of the infrared continuum in Seyfert 2 galaxies is not well understood. An attractive model is one in which dust grains near the nucleus are heated by optical and ultraviolet photons from a central source and ... -
Nuclear rings in active galaxies
(1996) [Artigo de periódico]We investigate two current problems in active galactic nuclei-the mode of fueling the putative black hole, and the question of whether the circumnuclear regions have experienced unusual chemical processing-by studying the ... -
Photoionization of very high excitation gas in circinus galaxy and other active galactic nuclei
(1997) [Artigo de periódico]Recent measurements of the Circinus galaxy with ISO by Moorwood et al. (1996) have confirmed the extremely high excitation of the emission-line spectrum in this active galaxy. Moorwood et al. modelled the spectrum in terms ... -
Radiatively inefficient accretion flow in the nucleus of NGC 1097
(2006) [Artigo de periódico]We present a model for the accretion flow around the supermassive black hole in the LINER nucleus of NGC 1097 that fits the optical to X-ray spectral energy distribution (SED). The X-ray segment of the SED is based on ... -
The ionization cone, obscured nucleus, and gaseous outflow in NGC 3281 : a prototypical Seyfert 2 galaxy?
(1992) [Artigo de periódico]We present narrow-band images and long-slit spectroscopy of the central region of the highly inclined Seyfert galaxy NGC 3281. The image of the continuum-subtracted [O III] λ4959 emission line shows a very clear conical ... -
The temperature of extended gas in active galaxies : evidence for matter-bounded clouds
(1997) [Artigo de periódico]We report measurements of the electron temperature at about a dozen locations in the extended emission-line regions of five active (Seyfert and radio) galaxies. Temperatures (T[O III] and T[N II]) have been determined from ... -
The variability of the double-peaked balmer lines in the active nucleus of NGC 1097
(1995) [Artigo de periódico]We present spectroscopic observations of the nucleus of the Seyfert/low-ionization nuclear emission-line region galaxy NGC 1097 spanning the period 1991-1994. The goal was to monitor anticipated variations of the broad, ...
