Constraints on $\tau_\mathrm{NL}$ from Planck temperature and polarization

Abstract

We update constraints on the amplitude of the primordial trispectrum, using the final Planck mission temperature and polarization data. In the squeezed limit, a cosmological local trispectrum would be observed as a spatial modulation of small-scale power on the CMB sky. We reconstruct this signal as a source of statistical anisotropy via quadratic estimator techniques. We systematically demonstrate how the estimated power spectrum of a reconstructed modulation field can be translated into a constraint on $\tau_\mathrm{NL}$ via likelihood methods, demonstrating the procedures effectiveness by inferring known $\tau_\mathrm{NL}$ signal(s) from simulations. Our baseline results constrain $\tau_\mathrm{NL} < 1700$ at the 95\% confidence level, providing the most stringent constraints to date.