Digital.CSIC > Ciencia y Tecnologías Físicas > Instituto de Física de Cantabria (IFCA) > (IFCA) Artículos >

Open Access item Quasar-galaxy associations revisited

Authors:Benítez, Narciso
Sanz, J. L.
Martínez-González, Enrique
Keywords:Quasar galaxy associations, Gravitational lensing
Issue Date:24-Aug-2000
Publisher:Blackwell Publishing
Mon. Not. Roy. Astron. Soc. 320 (2001) 241
Abstract:Gravitational lensing predicts an enhancement of the density of bright, distant QSOs around foreground galaxies. We measure this QSO-galaxy correlation w_qg for two complete samples of radio-loud quasars, the southern 1Jy and Half-Jansky samples. The existence of a positive correlation between z~1 quasars and z~0.15 galaxies is confirmed at a p=99.0% significance level (>99.9%) if previous measurements on the northern hemisphere are included). A comparison with the results obtained for incomplete quasar catalogs (e.g. the Veron-Cetty and Veron compilation) suggests the existence of an `identification bias', which spuriously increases the estimated amplitude of the quasar-galaxy correlation for incomplete samples. This effect may explain many of the surprisingly strong quasar-galaxy associations found in the literature. Nevertheless, the value of w_qg that we measure in our complete catalogs is still considerably higher than the predictions from weak lensing. We consider two effects which could help to explain this discrepancy: galactic dust extinction and strong lensing.
Description:9 pages, 6 figures.-- MNRAS accepted.
Appears in Collections:(IFCA) Artículos

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.