Blinding scheme for the scale-dependence bias signature of local primordial non-Gaussianity for DESI 2024

TL;DR

This paper introduces a blinding method at the density field level to prevent confirmation bias in measuring local primordial non-Gaussianity, crucial for upcoming spectroscopic surveys like DESI.

Contribution

A novel blinding technique that generates weights to mask the scale-dependent bias signature, ensuring unbiased analysis of primordial non-Gaussianity in large-scale structure data.

Findings

Validated through simulations mimicking DESI data

Compatible with other catalog-level blinding procedures

Effective in preventing bias in non-Gaussianity measurements

Abstract

The next generation of spectroscopic surveys is expected to achieve an unprecedented level of accuracy in the measurement of cosmological parameters. To avoid confirmation bias and thereby improve the reliability of these results, blinding procedures become a standard practice in the cosmological analyses of such surveys. Blinding is especially crucial when the impact of observational systematics is important relative to the cosmological signal, and a detection of that signal would have significant implications. This is the case for local primordial non-gaussianity, as probed by the scale-dependent bias of the galaxy power spectrum at large scales that are heavily sensitive to the dependence of the target selection on the imaging quality, known as imaging systematics. We propose a blinding method for the scale-dependent bias signature of local primordial non-gaussianity at the density field level which consists in generating a set of weights for the data that replicate the scale-dependent bias. The applied blinding is predictable, and can be straightforwardly combined with other catalog-level blinding procedures that have been designed for the baryon acoustic oscillation and redshift space distortion signals. The procedure is validated through simulations that replicate data from the first year of observation of the Dark Energy Spectroscopic Instrument, but may find applications to other upcoming spectroscopic surveys.