QSO-galaxy correlations: Lensing or dust?

We present evidence for an anti-correlation between faint QSOs and B < 23 g alaxies. A sample of 192 QSOs in a 2.5 deg(2) area has been imaged using th e Isaac Newton Telescope Wide-Field Camera. The cross-correlation signal is of a similar amplitude to the galaxy auto-correlation function at the limi t of B < 23, but is negative in sign, As fainter galaxies are selected the negative correlation signal becomes less significant, until the signal is e ffectively zero at B < 26. We propose two alternate explanations for the ob served effect. The first is gravitational lensing of the faint background Q SOs, which have a flat number count slope. However, the lensing signal is s ignificantly higher than expected in conventional models. The second possib ility is that inter-galactic dust absorption is responsible. A reddening of only E(B - V) <similar or equal to> 0.02 is required to produce the observ ed correlation. The large 2dF and SDSS QSO surveys should allow a definitiv e solution to the question of QSO-galaxy correlations.