|
|||||
|
|
Host galaxy morphologies of X-ray selected AGN: assessing the significance of different black hole fuelling mechanisms to the accretion density of the Universe at z∼ 1. |
|
| Authors: | A Georgakakis A L Coil E S Laird R L Griffith K Nandra J M Lotz C M Pierce M C Cooper J A Newman A M Koekemoer |
| Institution: | National Observatory of Athens, V. Paulou and I. Metaxa, 11532, Greece;Department of Physics and Center for Astrophysics and Space Sciences, University of California, 9500 Gilman Dr., La Jolla, San Diego, CA 92093, USA;Astrophysics Group, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ;Jet Propulsion Laboratory, California Institure of Technology, Pasadena, CA 91109, USA;National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA;Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064, USA;Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721-0065, USA;University of Pittsburgh, Physics and Astronomy Department, 3941 O'Hara Street, Pittsburgh, PA 15260, USA;Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA |
| Abstract: | We use morphological information of X-ray selected active galactic nuclei (AGN) hosts to set limits on the fraction of the accretion density of the Universe at z ≈ 1 that is not likely to be associated with major mergers. Deep X-ray observations are combined with high-resolution optical data from the Hubble Space Telescope in the All-wavelength Extended Groth strip International Survey, Great Observatories Origins Deep Survey (GOODS) North and GOODS South fields to explore the morphological breakdown of X-ray sources in the redshift interval 0.5 < z < 1.3 . The sample is split into discs, early-type bulge-dominated galaxies, peculiar systems and point sources in which the nuclear source outshines the host galaxy. The X-ray luminosity function and luminosity density of AGN at z ≈ 1 are then calculated as a function of morphological type. We find that disc-dominated hosts contribute 30 ± 9 per cent to the total AGN space density and 23 ± 6 per cent to the luminosity density at z ≈ 1 . We argue that AGN in disc galaxies are most likely fuelled not by major merger events but by minor interactions or internal instabilities. We find evidence that these mechanisms may be more efficient in producing luminous AGN |
| Keywords: | surveys galaxies: evolution galaxies: starbursts X-rays: galaxies |