The Low-Redshift Quasar-Quasar Correlation Function from an Extragalactic Halpha Emission-Line Survey to z=0.4

We study the large-scale spatial distribution of low-redshift quasars and luminous Seyfert~1 galaxies using a sample of 108 AGN (0.2 < z < 0.37) selected in a far-red (6000 to 9200\AA) H$\alpha$ emission-line survey. There are 19 pairs of AGN with comoving separations $r < 20 \hmpc$ ($\Omega = 1$). Using Monte Carlo simulations we reject the hypothesis that these pairs were drawn from a random sample at the 99.97% confidence level. We apply simple evolution models to compare the measured correlation function amplitude, $A = 0.4 \cdot \bar{\xi}(r < 15 \hmpc) \cdot 15^{1.8} = 125 \pm 51$, to that of galaxy systems in the local universe and quasars at z > 1. We infer that quasars and luminous Seyfert~1 at $z \lesssim 0.3$ are useful tracers of the large-scale structure, with a bias comparable to groups of galaxies. We find a decrease in the quasar clustering amplitude by a factor of $4.6\pm1.9$ between z = 0.26 and $z \approx 1.5$.