Jean-Pierre Lasota
Institut d'Astrophysique de Paris (Paris, France)
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
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| « Radio Loudness of AGNs: Host Galaxy Morphology and the so-called Spin Paradigm » |
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Jean-Pierre Lasota |
| When investigating how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass one finds that AGNs form two distinct and well separated sequences on the radio-loudness - Eddington-ratio (bolometric luminosity in Eddington units) plane. These sequences mark the real upper bounds of radio-loudness of two distinct populations of AGNs: those hosted respectively by elliptical and disk galaxies. Both sequences show the same dependence of the radio-loudness on the Eddington ratio (an increase with decreasing Eddington ratio), which suggests that another parameter in addition to the accretion rate must play a role in determining the jet production efficiency in active galactic nuclei, and that this parameter is related to properties of the host galaxy. The revealed host-related radio dichotomy breaks down at high accretion rates where the dominant fraction of luminous quasars hosted by elliptical galaxies is radio quiet. The huge difference between the radio-loudness reachable by AGNs in disc and elliptical galaxies can be explained by the scenario according to which the spin of a black hole determines the outflow's power, and central black holes can reach large spins only in early type galaxies, and not (in a statistical sense) in spiral galaxies. Uncertainties and difficulties of this and other scenarios will be presented and discussed. |
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vendredi 24 octobre 2008 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |