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Associations between Galaxies and Bright Quasars1

Published online by Cambridge University Press:  25 April 2016


M. J. Drinkwater
Affiliation:
Anglo-Australian Observatory, Coonabarabran, NSW 2357
R. L. Webster
Affiliation:
School of Physics, University of Melbourne, Parkville, Vic 3052
P. A. Thomas
Affiliation:
MAPS, University of Sussex, Brighton BN1 9QH, UK
D. Millar
Affiliation:
Department of Astronomy, University of Toronto, Toronto, Ont M5S 1A1, Canada

Abstract

The results of a new imaging survey of 68 bright (mv < 18) high redshift (z > 0.7) quasars are presented. The distribution of celestial distances between the quasars and the nearest galaxy neighbours shows an excess at small separations (< 15 arcseconds) significant at the 99.96% level. The redshifts of these galaxies are not known, so two interpretations are possible. If the galaxies are in groups physically associated with the quasars then they must be significantly brighter (> 3 magnitudes) than normal M* galaxies at the present epoch. Alternatively, this may be the result of a bias caused by gravitational amplification of background quasars by compact lenses in the halos of the nearest neighbour (foreground) galaxies. Of the present sample, 25% of the quasars have extra galaxies. If this is caused by a gravitational lensing bias, then, allowing for incompleteness, the results imply that as many as 60% of bright quasars may be gravitationally lensed.


Type
Invited
Copyright
Copyright © Astronomical Society of Australia 1992

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Footnotes

1.

Based on observations made at Observatoire du Mont Mégantic, Université Laval, Québec, Canada.


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