Binary Quasars in the Sloan Digital Sky Survey: Evidence for Excess Clustering on Small Scales

We present a sample of 218 new quasar pairs with proper transverseseparations R_prop < 1 Mpc/h over the redshift range 0.5 < z < 3.0, discoveredfrom an extensive follow up campaign to find companions around the SloanDigital Sky Survey and 2dF Quasar Redshift Survey quasars. This sample includes26 new binary quasars with separations R_prop < 50 kpc/h (theta < 10arcseconds), more than doubling the number of such systems known. We define astatistical sample of binaries selected with homogeneous criteria and computeits selection function, taking into account sources of incompleteness. Thefirst measurement of the quasar correlation function on scales 10 kpc/h 3 Mpc/h quasar correlation function, extrapolated down as a power law to theseparations probed by our binaries. The excess grows to ~ 30 at R_prop ~ 10kpc/h, and provides compelling evidence that the quasar autocorrelationfunction gets progressively steeper on sub-Mpc scales. This small scale excesscan likely be attributed to dissipative interaction events which trigger quasaractivity in rich environments. Recent small scale measurements of galaxyclustering and quasar-galaxy clustering are reviewed and discussed in relationto our measurement of small scale quasar clustering.Comment: 25 pages, 12 figures, 9 tables. Submitted to the Astronomical Journa