Observational systematics can strongly bias clustering measurements on large scales, which can mimic cosmologically relevant signals such as deviations from Gaussianity in the spectrum of primordial perturbations. We measure the angular clustering of photometrically classified quasars using an optimal quadratic estimator in four redshift slices with an accuracy of ~ 25% over a bin width of δl ~ 10−15 on scales corresponding to matter-radiation equality and larger (0ℓ ~ 2−3). In principle, such a large volume and medium density of tracers should facilitate high-precision cosmological constraints. This data set spans 0~ 11,00 square degrees and probes a volume of 80 h⁻³ Gpc³. We present the large-scale clustering of 1.6 million quasars between z=0.5 and z=2.5 that have been classified from this imaging, representing the highest density of quasars ever studied for clustering measurements. The Sloan Digital Sky Survey has surveyed 14,555 square degrees of the sky, and delivered over a trillion pixels of imaging data.
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