The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: analysis of potential systematics

Abstract

We analyze the density field of galaxies observed by the Sloan Digital Sky\nSurvey (SDSS)-III Baryon Oscillation Spectroscopic Survey (BOSS) included in\nthe SDSS Data Release Nine (DR9). DR9 includes spectroscopic redshifts for over\n400,000 galaxies spread over a footprint of 3,275 deg^2. We identify,\ncharacterize, and mitigate the impact of sources of systematic uncertainty on\nlarge-scale clustering measurements, both for angular moments of the\nredshift-space correlation function and the spherically averaged power\nspectrum, P(k), in order to ensure that robust cosmological constraints will be\nobtained from these data. A correlation between the projected density of stars\nand the higher redshift (0.43 < z < 0.7) galaxy sample (the `CMASS' sample) due\nto imaging systematics imparts a systematic error that is larger than the\nstatistical error of the clustering measurements at scales s > 120h^-1Mpc or k\n< 0.01hMpc^-1. We find that these errors can be ameliorated by weighting\ngalaxies based on their surface brightness and the local stellar density. We\nuse mock galaxy catalogs that simulate the CMASS selection function to\ndetermine that randomly selecting galaxy redshifts in order to simulate the\nradial selection function of a random sample imparts the least systematic error\non correlation function measurements and that this systematic error is\nnegligible for the spherically averaged correlation function. The methods we\nrecommend for the calculation of clustering measurements using the CMASS sample\nare adopted in companion papers that locate the position of the baryon acoustic\noscillation feature (Anderson et al. 2012), constrain cosmological models using\nthe full shape of the correlation function (Sanchez et al. 2012), and measure\nthe rate of structure growth (Reid et al. 2012). (abridged)\n