Optimal constraints on Primordial non-Gaussianity with the eBOSS DR16 quasars in Fourier space

TL;DR

This paper constrains primordial non-Gaussianity using quasar data from SDSS DR16, employing optimal weighting techniques to improve bounds and explore systematic effects in large-scale structure measurements.

Contribution

It introduces an optimal weighting method for analyzing quasar power spectra to tighten constraints on local PNG, revealing potential systematic effects in the data.

Findings

Constraints on $f_{NL}$: -4 to 27 at 68% CL.

Optimal weighting reduces error bars by about 10%.

Systematic effects may limit the improvement of constraints.

Abstract

We present constraints on the amplitude of local Primordial Non-Gaussianities (PNG), $f_{\rm NL}$, using the quasar sample in the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 16. We analyze the power spectrum monopole, testing for the presence of scale dependent galaxy bias induced by local PNG. Our analysis makes use of optimal redshift weights that maximize the response of the quasar sample to the possible presence of non zero PNG. We find $-4<f_{\rm NL}<27$ at $68\%$ confidence level, which is among the strongest bounds with Large Scale Structure data. The optimal analysis reduces the error bar by about 10% compared to the standard one, an amount which is smaller than what was expected from a Fisher matrix analysis. This, and the reduced improvement over previous releases of the same catalog, suggest the presence of still unknown systematic effects in the data. If the quasars have a lower response to local PNG, our optimal constraint becomes $-23<f_{\rm NL}<21$ at $68\%$, with an improvement of $30\%$ over standard analyses. We also show how to use the optimal weights to put data-driven priors on the sample's response to local PNG.