Galaxy imaging surveys as spin-sensitive detector for cosmological colliders

TL;DR

Galaxy imaging surveys can serve as spin-sensitive detectors for primordial non-Gaussianity caused by higher spin particles during inflation, offering a new probe of early universe physics.

Contribution

This work introduces a systematic method to decompose galaxy shapes into spin components and demonstrates their sensitivity to spin-dependent primordial non-Gaussianity.

Findings

Galaxy shapes are sensitive to primordial non-Gaussianity from higher spin particles.

Galaxy surveys can detect spin-dependent signals in the early universe.

Forecasts suggest upcoming surveys can constrain such primordial signals.

Abstract

Galaxy imaging surveys provide us with information on both the galaxy distribution and their shapes. In this paper, we systematically investigate the sensitivity of galaxy shapes to new physics in the initial conditions. For this purpose, we decompose the galaxy shape function into spin components, and compute the contributions to each spin component from both intrinsic alignment and weak lensing. We then consider the angular-dependent primordial non-Gaussianity, which is generated by a non-zero integer spin particle when active during inflation, and show that a galaxy imaging survey essentially functions as a spin-sensitive detector of such particles in the early universe. We also perform a forecast of the PNG generated from a higher spin particle, considering a Rubin Observatory LSST-like galaxy survey.