Eddington ratios of faint AGN at intermediate redshift: evidence for a population of half-starved black holes^*

¹ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: igavignaud@aip.de
² Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstr., 85741 Garching, Germany
³ Integral Science Data Centre, Ch. d'Écogia 16, 1290 Versoix, Switzerland
⁴ Geneva Observatory, Ch. des Maillettes 51, 1290 Sauverny, France
⁵ INAF-Osservatorio Astronomico di Bologna, via Ranzani, 1, 40127, Bologna, Italy
⁶ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁷ Laboratoire d'Astrophysique de Marseille (UMR6110), CNRS-Université de Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13, France
⁸ Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue Édouard Belin, 31400 Toulouse, France
⁹ IASF-INAF, via Bassini 15, 20133, Milano, Italy
¹⁰ IRA-INAF, via Gobetti,101, 40129, Bologna, Italy
¹¹ INAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
¹² INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
¹³ Institut d'Astrophysique de Paris, UMR 7095, 98bis Bvd. Arago, 75014 Paris, France
¹⁴ School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG72RD, UK INAF-Osservatorio Astronomico di Brera, via Brera 28, Milan, Italy
¹⁵ Canada France Hawaii Telescope corporation, Mamalahoa Hwy, Kamuela, 96743, USA
¹⁶ Observatoire de Paris, LERMA, 61 avenue de l'Observatoire, 75014 Paris, France
¹⁷ Università di Bologna, Dipartimento di Astronomia, via Ranzani, 1, 40127, Bologna, Italy
¹⁸ Università di Milano-Bicocca, Dipartimento di Fisica, Piazza delle Scienze, 3, 20126 Milano, Italy

Received: 29 October 2007
Accepted: 17 October 2008

Abstract

We use one of the deepest spectroscopic samples of broad-line active galactic nuclei (AGN) currently available, extracted from the VIMOS VLT Deep Survey (VVDS), to compute the and virial-mass estimates of 120 super-massive black holes in the redshift range and . We find that the mass-luminosity relation shows considerably enhanced dispersion towards low AGN luminosities (). At these luminosities, there is a substantial fraction of black holes accreting far below their Eddington limit (), in marked contrast to what is generally found for AGN of higher luminosities. We speculate that these may be AGN on the decaying branch of their lightcurves, well past their peak activity. This would agree with recent theoretical predictions of AGN evolution. In the electronic Appendix of this paper we publish an update of the VVDS type-1 AGN sample, including the first and most of the second-epoch observations. This sample contains 298 objects of which 168 are new.