Cosmological constraints from the nonlinear galaxy bispectrum

We present the cosmological constraints from analyzing higher-order galaxy clustering on small nonlinear scales. We use SimBIG, a forward modeling framework for galaxy clustering analyses that employs simulation-based inference to perform highly efficient cosmological inference using normalizing flows. It leverages the predictive power of high-fidelity simulations and robustly extracts cosmological information from regimes inaccessible with current standard analyses. In this work, we apply SimBIG to a subset of the BOSS galaxy sample and analyze the redshift-space bispectrum monopole, ${B}_{0}({k}_{1},{k}_{2},{k}_{3})$, to ${k}_{\mathrm{max}}=0.5\text{ }\text{ }h/\mathrm{Mpc}$. We achieve $1\ensuremath{\sigma}$ constraints of ${\mathrm{\ensuremath{\Omega}}}_{m}=0.29{3}_{\ensuremath{-}0.027}^{+0.027}$ and ${\ensuremath{\sigma}}_{8}=0.78{3}_{\ensuremath{-}0.038}^{+0.040}$, which are more than 1.2 and $2.4\ifmmode\times\else\texttimes\fi{}$ tighter than constraints from standard power spectrum analyses of the same dataset. We also derive 1.4, 1.4, $1.7\ifmmode\times\else\texttimes\fi{}$ tighter constraints on ${\mathrm{\ensuremath{\Omega}}}_{b}$, $h$, ${n}_{s}$. This improvement comes from additional cosmological information in higher-order clustering on nonlinear scales and, for ${\ensuremath{\sigma}}_{8}$, is equivalent to the gain expected from a standard analysis on a $\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}$ larger galaxy sample. Even with our BOSS subsample, which only spans 10% of the full BOSS volume, we derive competitive constraints on the growth of structure: ${S}_{8}=0.77{4}_{\ensuremath{-}0.053}^{+0.056}$. Our constraint is consistent with results from both cosmic microwave background and weak lensing. Combined with a ${\ensuremath{\omega}}_{b}$ prior from big bang nucleosynthesis, we also derive a constraint on ${H}_{0}={67.6}_{\ensuremath{-}1.8}^{+2.2}\text{ }\text{ }\mathrm{km}\text{ }{\mathrm{s}}^{\ensuremath{-}1}\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$ that is consistent with early Universe constraints.

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