Testing the ADAF paradigm for supermassive black holes in elliptical galaxies |
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| Institution: | 1. Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, Pessac, 33615, France;2. Instituto de Ciencias de Materiales de Madrid (CSIC), Madrid, 28049, Spain;3. LERMA, Obs. de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, ENS, F-75005, France;4. Faculty of Aerospace Engineering, Delft University of Technology, Delft, Netherlands;5. Leiden Observatory, Leiden University, P.O. Box 9513, Leiden, NL 2300 RA, Netherlands;6. LERMA, Université de Cergy Pontoise, Sorbonne Universités, UPMC Univ. Paris 6, PSL Research University, Observatoire de Paris, UMR 8112 CNRS, 5 mail Gay Lussac 95000 Cergy Pontoise, France;7. CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Aix Marseille Univ, Marseille, France;8. Sorbonne Universités, UPMC Univ. Paris 6 & CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, Paris, 75014, France;9. Institut d’Astrophysique Spatiale, Univ. Paris-Sud & CNRS, Univ. Paris-Saclay - IAS, bâtiment 121, univ Paris-Sud, Orsay, 91405, France;10. Dept. Physics and Astronomy, Aarhus University, Ny Munkegade 120, Aarhus C, 8000, Denmark;11. Institut des Sciences Moléculaires d’Orsay, ISMO, CNRS, Université Paris-Sud, Université Paris Saclay, Orsay, F-91405, France;12. Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, SE 412 96, Sweden;13. Dipartimento di Fisica e Astronomia, Universitá di Catania, Via S. Sofia 64, Catania, 95123 Sicily, Italy;14. Chemistry Department, University College London, 20 Gordon Street, London WC1H 0AJ, UK;15. Laboratoire AIM, Paris-Saclay, CEA/IRFU/DAp - CNRS, Université Paris Diderot, Gif-sur-Yvette Cedex, 91191, France;p. 201 Physics Bldg., Syracuse University, Syracuse, NY, 13244, USA;q. Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido, 060-0819, Japan |
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| Abstract: | The growing evidence for supermassive black holes in the centres of nearby galaxies has brought into sharper focus the question of why elliptical galaxies, rich in hot gas, do not possess quasar-like luminosities. Recent studies suggest that the presence of advection-dominated accretion flows (ADAFs) with their associated low radiative efficiency, might provide a promising explanation for the observed quiescence of these systems. Here, we present new high-frequency radio observations of the three giant, low-luminosity elliptical galaxies NGC 4649, NGC 4472 and NGC 4636 obtained using the Very Large Array (VLA) and the sub-millimetre common-user bolometer array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). The new radio limits disagree severely with the canonical ADAF predictions which significantly overestimate the observed flux. If the accretion in these objects occurs in an advection-dominated mode then our radio limits imply that the emission from their central regions must be suppressed. We present the possibility that the magnetic field in the flow is extremely low or that synchrotron emission is free-free absorbed by cold material in the accretion flow. We also discuss whether slow non-radiating accretion flows may drive winds/outflows to remove energy, angular momentum and mass so that the central densities, pressures and emissivities are much smaller than in a standard ADAF (Di Matteo et al. 1998). |
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