Multiwavelength study of the nuclei of a volume-limited sample of galaxies – II. Optical, infrared and radio observations |
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| Authors: | P Lira R A Johnson A Lawrence R Cid Fernandes |
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| Institution: | Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile;Astrophysics, Oxford University, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH;SUPA1?, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ;Departamento de de Física –CFM –Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil |
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| Abstract: | We present optical and infrared broad-band images, radio maps, and optical spectroscopy for the nuclear region of a sample of nearby galaxies. The galaxies have been drawn from a complete volume-limited sample for which we have already presented X-ray imaging. We modelled the stellar component of the spectroscopic observations to determine the star formation history of our targets. Diagnostic diagrams were used to classify the emission-line spectra and determine the ionizing mechanism driving the nuclear regions. All those sources classified as active galactic nuclei present small Eddington ratios (～10?3–10?6) , implying a very slow growth rate of their black holes. We finally investigate the relative numbers of active and normal nuclei as a function of host galaxy luminosity and find that the fraction of active galaxies slowly rises as a function of host absolute magnitude in the M B ～?12 to ?22 range. |
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| Keywords: | galaxies: active galaxies: general galaxies: nuclei |
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