Abstract
We have investigated the proposed correlations between the positions of high-redshift QSOs and low-redshift galaxies using unbiased catalogues of UVX objects and galaxies selected from machine measurements of photographic plates. In no case do we find evidence for an excess of high-redshift QSOs around low-redshift galaxies. Indeed, we find a significant (4σ) 30 per cent deficiency of UVX objects at separations of less than 4arcmin from galaxies lying in clusters. This anti-correlation is most simply explained by a model in which dust situated in foreground clusters of galaxies obscures the QSOs lying behind them, consistent with the cosmological interpretation of QSO redshifts. An absorption of |$A_B=0.2$| mag is sufficient to produce the observed effect. The amount of dust required to give this level of absorption is small (|$10^{10}M_\odot$| per cluster). This dust can survive significant sputtering by hot gas in clusters of galaxies and is well within limits placed on its existence by intergalactic reddening results.
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