Scale-Dependent Galaxy Bias from Massive Particles with Spin during Inflation

TL;DR

This paper explores how upcoming galaxy surveys can detect signatures of massive particles with spin during inflation through their impact on galaxy bias, providing a new way to probe early universe particle content.

Contribution

It demonstrates the potential of galaxy power spectrum measurements and multi-tracer techniques to constrain the properties of particles with spin during inflation.

Findings

Constraints on spin 0 and 1 particles are promising.

Constraining spin 2 particles from power spectrum alone is challenging.

Gravitational non-linearities affect constraints by less than a factor of 2.

Abstract

The presence of additional particles during inflation leads to non-Gaussianity in late-time correlators of primordial curvature perturbations. The shape and amplitude of this signal depend on the mass and spin of the extra particles. Constraints on this distinct form of primordial non-Gaussianity, therefore, provide a wealth of information on the particle content during inflation. We investigate the potential of upcoming galaxy surveys in constraining such a signature through its impact on the observed galaxy power spectrum. Primordial non-Gaussianity of various shapes induces a scale-dependent bias on tracers of large-scale structure, such as galaxies. Using this signature we obtain constraints on massive particles during inflation, which can have non-zero spins. In particular, we show that the prospects for constraining particles with spins 0 and 1 are promising, while constraining particles with spin 2 from power spectrum alone seems challenging. We show that the multi-tracer technique can significantly improve the constraints from the power spectrum by at least an order of magnitude. Furthermore, we analyze the effect of non-linearities due to gravitational evolution on the forecasted constraints on the masses of the extra particles and the amplitudes of the imprinted non-Gaussian signal. We find that gravitational evolution affects the constraints by less than a factor of 2.