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

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 $f_{\mathrm{NL}}^{\mathrm{loc}}$ 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 $f_{\mathrm{NL}}^{\mathrm{loc}}$ constraints, by $\sim 9\%$ to a measurement of $f_{\mathrm{NL}}^{\mathrm{loc}}=2.1_{-8.3}^{+8.8}$ 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 $\sim 8\%$ 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 $f_{\mathrm{NL}}^{\mathrm{loc}}$ through its cross-correlation in preparation for future DESI data analyses.

26 pages, 6 figures, 7 tables