Local primordial non-Gaussianity using cross-correlations of DESI tracers

TL;DR

This study uses cross-correlations of DESI tracers to constrain local primordial non-Gaussianity, finding that certain cross-correlations improve measurement precision and serve as a preparatory step for future analyses.

Contribution

It demonstrates the potential of cross-correlations between different DESI tracers to improve constraints on primordial non-Gaussianity, especially between LRGs and quasars.

Findings

Cross-correlation between LRGs and quasars improves $f^ ext{loc}_ ext{NL}$ constraints by ~9%.

Including DESI ELG sample does not significantly improve constraints.

Mock tests predict an additional ~8% gain in measurement precision.

Abstract

We constrain local primordial non-Gaussianity by a combined analysis of auto and cross-correlations of DESI DR1 tracers, leveraging LRGs and QSOs as well as ELGs between $0.8<z<3.1$. By cross-validating the signal across different clustering tracers within the same redshift range, we evaluate potential systematics in the $f^\mathrm{loc}_\mathrm{NL}$ measurements, capitalizing on the reduced susceptibility of cross-correlations to non-common systematics. We find that the cross-correlation between LRG and quasars can robustly improve the DESI DR1 $f^\mathrm{loc}_\mathrm{NL}$ constraints, by $\sim9\%$ to a measurement of $f^\mathrm{loc}_\mathrm{NL}=2.1_{-8.3}^{+8.8}$ at 68\% confidence. On the other hand, we do not find a clear improvement when including the DESI DR1 ELG sample. Mock tests predict an additional $\sim8\%$ gain with statistical scatter, and the lack of improvement in the data remains consistent with this expectation. This project serves as an exploratory analysis of DESI ELG clustering for $f^\mathrm{loc}_\mathrm{NL}$ through its cross-correlation in preparation for future DESI data analyses.