Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 397, Issue 2, Pages 623-633Publisher
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2009.14951.x
Keywords
surveys; galaxies: evolution; galaxies: starbursts; X-rays: galaxies
Categories
Funding
- NASA through the Spitzer Space Telescope Fellowship Program
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [0806732] Funding Source: National Science Foundation
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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 approximate to 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 approximate to 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 approximate to 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 (L-X > 10(44)erg s(-1)) compared to predictions for the stochastic fuelling of massive black holes in disc galaxies.
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