A search for quasars in a field around NGC 520

Abstract

Summary We have performed an objective-prism search for quasars in a field around the galaxy NGC 520. The AUTOMATED QUASAR DETECTION (AQD) software has been applied and a sample of 175 highly rated quasar candidates has been selected and is presented here. The 2D and 3D distributions of the candidates have been analysed. The distribution on the celestial sphere turns out to be non-random. The deviations from randomness are both a tendency to exhibit anticorrelation at the scale of a few arcmin and a significant excess of objects at separations of about 20 arcmin. A very weak tendency towards spatial clustering is also detected (significance level 0.04) at a typical scale of 10 h−1 Mpc, but it concerns an extremely small number of candidates and a definitive conclusion is delayed until all the candidates have been observed spectroscopically. Finally, in order to test the claims by Arp & Duhalde that an excess of quasars exists near NGC 520 and that there is a preferential NE-SW alignment of bright quasars across this amorphous galaxy, we have also performed various statistical analyses of the distribution of the high-grade quasar candidates with respect to NGC 520: no sign of any possible relation is present in our data.