S IMBIG: Cosmological Constraints from the Redshift-Space Galaxy Skew Spectra

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 S IMBIG forward modeling framework and simulation-based inference via normalizing flows, we analyze the CMASS-SGC sub-sample, which constitute approximately 10% of the full BOSS data. Analyzing the scales up to k_ max=0.5 Mpc^-1h, we find that the skew spectra improve the constraints on Ω_ m, Ω_ b, h, and n_s by 34%, 35%, 18%, 10%, respectively, compared to constraints from previous S IMBIG power spectrum multipoles analysis, yielding Ω_ m=0.288^+0.024_-0.034, Ω_ b= 0.043^+0.005_-0.007, h=0.759^+0.104_-0.050, n_ s = 0.918^+0.041_-0.090 (at 68% confidence limit). On the other hand, the constraints on σ_8 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^+0.034_-0.032, which is a 38% improvement over the constraint from the power spectrum with the same prior. Compared to the S IMBIG bispectrum (monopole) analysis, skew spectra offer comparable constraints on larger scales (k_ max<0.3 Mpc^-1h) for most parameters except for σ_8.