
%0 Journal Article
%A Croom, Scott M. 
%T QSO-Galaxy Correlations: Lensing or Dust?
%J Publications of the Astronomical Society of Australia
%D 2001/09/28
%V 18
%N 2
%P 169-171
%K gravitational lensing &#8212; galaxies: statistics &#8212; quasars: general &#8212; dust, extinction
%R https://doi.org/10.1071/AS01012
%U https://www.publish.csiro.au/paper/AS01012 
%X Received 2001 January 25, accepted 2001 May 3 We present evidence for an anti-correlation between faint QSOs and B &#60; 23 galaxies.A sample of 192 QSOs in a 2.5 deg2 area has been imaged using the Isaac Newton Telescope Wide-Field Camera. The cross-correlation signal is of a similar amplitude to the galaxy auto-correlation function at the limit of B &#60; 23, but is negative in sign. As fainter galaxies are selected the negative correlation signal becomes less significant, until the signal is effectively zero at B &#60; 26. We propose two alternate explanations for the observed effect. The first is gravitational lensing of the faint background QSOs, which have a flat number count slope. However, the lensing signal is significantly higher than expected in conventional models. The second possibility is that inter-galactic dust absorption is responsible. A reddening of only E(B - V) ~ 0.02 is required to produce the observed correlation. The large 2dF and SDSS QSO surveys should allow a definitive solution to the question of QSO&#8211;galaxy correlations. 
