The Low‐Redshift Quasar‐Quasar Correlation Function from an Extragalactic Hα Emission‐Line Survey toz = 0.4

We study the large-scale spatial distribution of low-redshift quasars and Seyfert~1 galaxies using a sample of 106 luminous emission-line objects ($ar{M}_{B} approx -23$) selected by their H$alpha$ emission lines in a far-red objective prism survey ($0.2 < z < 0.37$). Of the 106 objects, 25 were previously known AGN (Veron-Cetty and Veron 2000), and follow-up spectroscopy for an additional 53 objects (including all object pairs with separation $r < 20 hmpc$) confirmed 48 AGN and 5 narrow emission-line galaxies (NELGs). The calculated amplitude of the spatial two-point correlation function for the emission-line sample is $A = 0.4 cdot ar{xi}(r < 20 hmpc) cdot 20^{1.8} = 142 pm 53$. Eliminating the confirmed NELGs from the sample we obtain the AGN clustering amplitude $A = 98 pm 54$. 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 $3.7 pm 2.0$ between $z = 0.26$ and $z approx 1.5$, and present the coordinates, redshifts, and follow-up spectroscopy for the 15 previously unknown AGN and 4 luminous NELGs that contribute to the clustering signal.Comment: ApJ, in press, Vol 548, added follow-up spectroscop