$\mathrm{S}\mathrm{IM}\mathrm{BIG}$: 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 $\mathrm{S}\mathrm{IM}\mathrm{BIG}$ 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 $k_{\max }=0.5{\mathrm{Mpc}}^{-1}h$, we find that the skew spectra improve the constraints on ${\Omega }_{\mathrm{m}},{\Omega }_{\mathrm{b}},h$, and $n_s$ by 34\%, 35\%, 18\%, 10\%, respectively, compared to constraints from previous $\mathrm{S}\mathrm{IM}\mathrm{BIG}$ power spectrum multipoles analysis, yielding ${\Omega }_{\mathrm{m}}=0.288_{-0.034}^{+0.024}$, ${\Omega }_{\mathrm{b}}=0.043_{-0.007}^{+0.005}$, $h=0.759_{-0.050}^{+0.104}$, $n_{\mathrm{s}}=0.918_{-0.090}^{+0.041}$ (at 68\% confidence limit). On the other hand, the constraints on ${\sigma }_8$ 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 $h=0.750_{-0.032}^{+0.034}$, which is a 38\% improvement over the constraint from the power spectrum with the same prior. Compared to the $\mathrm{S}\mathrm{IM}\mathrm{BIG}$ bispectrum (monopole) analysis, skew spectra offer comparable constraints on larger scales ($k_{\max }<0.3{\mathrm{Mpc}}^{-1}h$) for most parameters except for ${\sigma }_8$.

23 pages, 12 figures, 2 tables