2001ApJ...548..585S

We study the large-scale spatial distribution of low-redshift quasars and Seyfert 1 galaxies using a sample of 106 luminous emission-line objects (M_B~-23) selected by their Hα emission lines in a far-red objective prism survey (0.2<z<0.37). Of the 106 objects, 25 were previously known active galactic nuclei (AGNs), and follow-up spectroscopy for an additional 53 objects (including all object pairs with separation r<20 h^–1 Mpc) confirmed 48 AGNs and 5 narrow emission line galaxies (NELGs). The calculated amplitude of the spatial two-point correlation function for the emission-line sample is A=0.4ξ(r<20 h^–1 Mpc)x20^1.8=142±53. Eliminating the confirmed NELGs from the sample, we obtain the AGN clustering amplitude A=98±54. Using Monte Carlo simulations, we reject the hypothesis that the observed pair counts were drawn from a random distribution at the 99.97% and 98.6% confidence levels for the entire sample and the AGN subset, respectively. We measure a decrease in the quasar clustering amplitude by a factor of 3.7±2.0 between z=0.26 and z~1.5, and present the coordinates, redshifts, and follow-up spectroscopy for the 15 previously unknown AGNs and four luminous NELGs that contribute to the clustering signal.