Intrinsic galaxy alignment from angular dependent primordial non-Gaussianity

TL;DR

This paper investigates how angular-dependent primordial non-Gaussianity, originating from massive spin fields and vector fields, influences galaxy alignment and cosmic shear, revealing scale-dependent effects and non-vanishing B-modes.

Contribution

It demonstrates the impact of massive spin-2 fields and vector fields on angular-dependent PNG, highlighting their effects on galaxy bias and cosmic shear patterns.

Findings

Angular-dependent PNG causes strong scale dependence in galaxy bias.

Massive spin-2 fields lead to distinctive scale-dependent galaxy alignment.

Vector field-induced PNG results in non-zero B-modes and non-diagonal shear components.

Abstract

In this paper, we explore a detectable imprint of massive fields with integer spins $s \geq 2$, which may be predicted from string theory. It was shown that such a massive non-zero spin field can generate the squeezed primordial bispectrum which depends on the angle between the two wavenumbers. We show that considering the contribution from the massive spin-2 field, the angular dependent primordial non-Gaussianity (PNG) yields a strong scale dependence in the bias parameter for the galaxy alignment, which becomes prominent at small scales. As another example of an angular dependent PNG, we also consider the primordial bispectrum where the angular dependence was introduced by a vector field, while breaking the global rotational symmetry. As a consequence, we find that the B-mode cosmic shear and non-diagonal components do not vanish. These aspects provide qualitative differences from the PNG sourced by massive non-zero spin fields.