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|Optical and Far-Infrared Emission of IRAS Seyfert Galaxies|
This paper presents an analysis of moderately large samples of type 1and 2 Seyfert galaxies through optical observations and far-infraredIRAS data, also taking into account theoretical color indices derivedfrom dust emission models. The galaxies in the samples cover a ratherlarge interval in far-infrared luminosity, i.e., 7.6 <= log(LIR/Lȯ) <= 12.6. We show that both types of Seyferts haveapproximately the same distribution of number of objects with a givenLIR. Galaxies with similar far-infrared color indices alpha (100, 60)are grouped together, and the corresponding average color indices areinterpreted in terms of a simple model in which the observed colorsresult from the combination of dust directly heated by the activegalactic nucleus with a component from the host galaxy represented bythe emission of cool dust. On the basis of the average IRAS colors ofthe derived groups, we show that type 1 and 2 Seyfert galaxies areundistinguishable from each other. From the luminosity ratios LIR/LHalpha and LIR/L[O III], we show that basically the same model can beapplied to both types of Seyfert, only allowing for the variation ofmodel conditions: type 2 Seyferts would be like type 1 Seyferts but withthe Seyfert nucleus and broad line region more effectively "hidden" bydust.
|An HI survey of late-type galaxies in the Southern Hemisphere. I - The SGC sample|
The present H I survey of Southern Hemisphere late-type galaxies wascompleted at the Nancay radio telescope between 1985 and 1988 and coverslarge galaxies selected from the Corwin et al. (1985) SGC catalog. Ofthe 311 galaxies observed, only 245 were detected due to the very lowsurface brightness of the Magellanic irregulars. These determinationsare conceived as useful for the establishment of distance criteria forlate-type galaxies. A histogram is presented of the velocities for thedetected galaxies vs morphological stages; attention is given toindividual spectra for 242 galaxies in the sample.
|Southern Galaxy Catalogue.|
|The Antlia cluster of galaxies and its environment - The Hydra I-Centaurus supercluster|
The small Antlia cluster of galaxies was investigated by measuring manyradial velocities for galaxies from the Lauberts catalog in the Antliaregion. Apart from the Antlia cluster itself, four more small groupswere identified. These five systems form a tiny but not bound Antliamini-supercluster. The mini-supercluster consists of small groups andclusters and of a dispersed component of field galaxies. The five galaxysystems are also part of the large Hydra I-Centaurus supercluster. Thislarge supercluster belongs now to the class of well observed ones. Ithas a chain-like filamentary structure. This supercluster seems to beconnected to the Local Supercluster via two very extended but very loosegroups. The total structure is the triangle-shaped Virgo-HydraI-Centaurus supercluster.
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