Cosmological constraints from the redshift-space galaxy skew spectra

Abstract

Extracting the non-Gaussian information of the cosmic large-scale structure (LSS) is vital in unlocking the full potential of the rich datasets from the upcoming stage-IV galaxy surveys. Galaxy skew spectra serve as efficient beyond-two-point statistics, encapsulating essential bispectrum information with computational efficiency akin to power spectrum analysis. This paper presents the first cosmological constraints from analyzing the full set of redshift-space galaxy skew spectra of the data from the SDSS-III BOSS, accessing cosmological information down to nonlinear scales. Employing the simbig forward modeling framework and simulation-based inference via normalizing flows, we analyze the CMASS-SGC subsample, which constitute approximately 10% of the full BOSS data. Analyzing the scales up to kmax=0.5 h-1 Mpc, we find that the skew spectra improve the constraints on ωm,ωb,h, and ns by 34%, 35%, 18%, 10%, respectively, compared to constraints from previous simbig power spectrum multipoles analysis, yielding ωm=0.288-0.034+0.024, ωb=0.043-0.007+0.005, h=0.759-0.050+0.104, ns=0.918-0.090+0.041 (at 68% confidence limit). On the other hand, the constraints on σ8 are weaker than from the power spectrum. Including the big bang nucleosynthesis (BBN) prior on baryon density reduces the uncertainty on the Hubble parameter further, achieving h=0.750-0.032+0.034, which is a 38% improvement over the constraint from the power spectrum with the same prior. Compared to the simbig bispectrum (monopole) analysis, skew spectra offer comparable constraints on larger scales (kmax<0.3 h-1 Mpc) for most parameters except for σ8.