Date Published:

January 1, 2013

Abstract:

We analyse the density field of 264 283 galaxies observed by the SloanDigital Sky Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey(BOSS) and included in the SDSS Data Release 9 (DR9). In total, the SDSSDR9 BOSS data include spectroscopic redshifts for over 400 000 galaxiesspread over a footprint of more than 3000 deg². We measurethe power spectrum of these galaxies with redshifts 0.43 < z < 0.7in order to constrain the amount of local non-Gaussianity,f{_N_L^local}, in the primordial density field, paying particularattention to the impact of systematic uncertainties. The BOSS galaxydensity field is systematically affected by the local stellar densityand this influences the ability to accurately measure f{_N_L^local}. Inthe absence of any correction, we find (erroneously) that theprobability that f{_N_L^local} is greater than zero, P(f{_N_L^local}> 0), is 99.5 per cent. After quantifying and correcting for thesystematic bias and including the added uncertainty, we find - 45 0) = 91.0 per cent. A more conservative approach assumes that wehave only learnt the k dependence of the systematic bias and allows anyamplitude for the systematic correction; we find that the systematiceffect is not fully degenerate with that of f{_N_L^local}, and wedetermine that -82 < f{_N_L^local} < 178 (at 95 per centconfidence) and P(f{_N_L^local} > 0) = 68 per cent. This analysisdemonstrates the importance of accounting for the impact of Galacticforegrounds on f{_N_L^local} measurements. We outline the methods thataccount for these systematic biases and uncertainties. We expect ourmethods to yield robust constraints on f{_N_L^local} for both our ownand future large-scale structure investigations.

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