Constraints on primordial non-Gaussianity from halo bias measured through CMB lensing cross-correlations

Local non-Gaussianities in the initial conditions of the Universe, parametrized by f(NL), induce a scale dependence in the large-scale bias of halos in the late Universe. This effect is a promising path to constrain multifield inflation theories that predict nonzero f(NL). While most existing constraints from the halo bias involve autocorrelations of the galaxy distribution, cross-correlations with probes of the matter density provide an alternative channel with fewer systematics. We present the strongest large-scale structure constraint on local primordial non-Gaussianity that utilizes cross-correlations alone. We use the cosmic infrared background (CIB) consisting of dusty galaxies as a halo tracer and cosmic microwave background (CMB) lensing as a probe of the underlying matter distribution, both from Planck data. Milky Way dust is one of the key challenges in using the large-scale modes of the CIB. Importantly, the cross-correlation of the CIB with CMB lensing is far less affected by Galactic dust compared to the autospectrum of the CIB, since the latter picks up an additive bias from Galactic dust. We find no evidence for primordial non-Gaussianity and obtain -87More