Skip to main content Accessibility help

Associations between Galaxies and Bright Quasars1

  • M. J. Drinkwater (a1), R. L. Webster (a2), P. A. Thomas (a3) and D. Millar (a4)


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.



Hide All

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



Hide All
Arnaud, J., Hammer, F., Jones, J. and Le Fevre, O., 1988, Astr. Astrophys., 206, L5.
Bergeron, J. and Boisse, P., 1991, Astr. Astrophys., 243, 344.
Blandford, R. D., 1990, Qrt. J. R. astr. Soc., 31, 305.
Colless, M., Ellis, R. S., Taylor, K. and Hook, R. N., 1990, Mon. Not. R. Astr. Soc., 244, 408.
Canizares, C. R., 1981, Nature, 291, 620.
Canizares, C. R., 1987, in IAU Symp. No. 124Observational Cosmology’, eds. Hewitt, A. et al. p.729.
Ellingson, E., Green, R. F. and Yee, H. K. C, 1991, Astrophys. J., in press.
Foltz, C.B., Weymann, R. J., Peterson, B. M., Sun, L., Malkan, M.A. and Chaffee, F. H., 1986, Astrophys. J., 307, 504.
Fugmann, W., 1988, Astr. Astrophys., 204, 73.
Fugmann, W., 1989, Astr. Astrophys., 222, 45.
Hewitt, A. and Burbidge, G., 1987, Astrophys. J. Suppl., 63, 1.
Hintzen, P., Romanishin, W. and Valdes, F., 1991, Astrophys. J., 366,7.
Irwin, M. J., Webster, R. L., Hewett, p. c., Corrigan, R. T. and Jedrzejewski, R. I., 1989. Astron. J., 98, 1989.
Millar, D., 1991, PhD thesis, University of Toronto.
Narayan, R., 1989, Astrophys. J., 339, L53.
Otrupcek, R. E. and Wright, A. E., 1990, Proc. Astron. Soc. Aust., 9, 170.
Sargent, W. L. W., Steidel, C. C. and Boksenberg, A., 1988, Astrophys. J., 334, 22.
Smith, E. P. and Heekman, T. M., 1990, Astrophys. J., 348, 38.
Tyson, J. A., 1986, Astron. J., 92, 691.
Tytler, D., Boksenberg, A., Sargent, W. L. W., Young, P. J. and Kunth, D., 1987, Astrophys. J. Suppl., 64, 667.
Valdes, F., 1982, FOCAS User’s Manual, (Tucson: KPNO).
Walsh, D., Carswell, R. F. and Weymann, R. J., 1979, Nature, 279, 381.
Webster, R. L., Hewett, P. C, Harding, M. E. and Wegner, G. A., 1988, Nature, 336, 358.
Webster, R. L. and Hewett, P. C, 1990, in Gravitational Lensing, eds. Mellier, et al. p.73.
Webster, R. L., 1991, to appear in the proceedings of the Quasar Workshop, held in Victoria, British Columbia, June 1991 (Pubi. Astr. Soc. Pacif., conf. series).
Wegner, G. and Swanson, S. R., 1990, Astron. J., 99, 330.
Weymann, R. J., Williams, R. E., Peterson, B. M. and Turnsheck, D. A., 1979, Astrophys. J., 234, 33.
Yee, H.K.C. and Green, R. F., 1987, Astrophys. J., 319, 28.
Young, P., Sargent, W. L. W. and Boksenberg, A., 1982, Astrophys. J. Suppl., 48, 455.


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed