New tests of dark sector interactions from the full-shape galaxy power spectrum

We explore the role of redshift-space galaxy clustering data in constraining nongravitational interactions between dark energy (DE) and dark matter (DM), for which state-of-the-art limits have so far been obtained from late-time background measurements. We use the joint likelihood for prereconstruction full-shape (FS) galaxy power spectrum and postreconstruction Baryon Acoustic Oscillation (BAO) measurements from the BOSS DR12 sample, alongside Cosmic Microwave Background (CMB) data from Planck: from this dataset combination we infer ${H}_{0}=68.0{2}_{\ensuremath{-}0.60}^{+0.49}\text{ }\text{ }\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ and the $2\ensuremath{\sigma}$ lower limit $\ensuremath{\xi}>\ensuremath{-}0.12$, among the strongest limits ever reported on the DM-DE coupling strength $\ensuremath{\xi}$ for the particular model considered. Contrary to what has been observed for the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model and simple extensions thereof, we find that the $\mathrm{CMB}+\mathrm{FS}$ combination returns tighter constraints compared to the $\mathrm{CMB}+\mathrm{BAO}$ one, suggesting that there is valuable additional information contained in the broadband of the power spectrum. We test this finding by running additional CMB-free analyses and removing sound horizon information, and discuss the important role of the equality scale in setting constraints on DM-DE interactions. Our results reinforce the critical role played by redshift-space galaxy clustering measurements in the epoch of precision cosmology, particularly in relation to tests of nonminimal dark sector extensions of the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model.

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