Chinese Journal of Astronomy and Astrophysics QSO-Galaxy Association and Gravitational Lensing

Abstract The amplification caused by gravitational light bending by compact objects in a foreground galaxy can affect the apparent number density of back-ground QSOs, as well as their distribution in the fields of galactic halos. In this work we investigate the number enhancement of QSOs in the fields of galactic ha-los caused by point mass lensing effect and singular isothermal lensing effect, and apply the micro-lensing effect due to dark compact objects in the halo to NGC 3628. NGC 3628 is a well-studied nearby edge-on Sbc peculiar galaxy, where QSOs are shown to be concentrated around the galaxy with a density much higher than background. We show that if present understanding of the luminosity function of QSOs is right, such concentration could not be caused by gravitational lensing