Galactic angular momenta and angular momentum couplings in the large-scale structure

TL;DR

This paper investigates the origin and correlations of galaxy angular momentum using a stochastic Gaussian process model, revealing how tidal shear and inertia interplay influence angular momentum alignments and their implications for weak lensing.

Contribution

It introduces a new model for angular momentum correlations that accounts for both tidal shear and inertia, distinguishing between parallel and antiparallel alignments.

Findings

Angular momentum scales as L/M ∝ M^{2/3}.

Milky Way-sized haloes show correlations on ~1 Mpc/h scales.

The correlation function fits an exponential form C_L(r) ∝ exp(-[r/r_0]^β).

Abstract

In this paper, we revisit the aquisition of angular momentum of galaxies by tidal shearing and compute the angular momentum variance sigma_L^2 as well as the angular momentum correlation function C_L(r) from a peak-restricted Gaussian random process. This stochastic process describing the initial conditions treats both the tidal shear as well as the inertia as dynamical fields and explicitly accounts for the discreteness of the inertia field. We describe the way in which the correlations in angular momentum result from an interplay of long-ranged correlations in the tidal shear, and short ranged correlations in the inertia field and which reflects the correlation between the eigensystems of these two symmetric tensors. We propose a new form of the angular momentum correlation function which is able to distinguish between parallel and antiparallel alignment of angular momentum vectors, and comment on implications of intrinsic alignments for weak lensing measurements. We confirm the scaling L/M propto. M^{2/3} and find the angular momentum distribution of Milky Way-sized haloes to be correlated on scales of ~1 Mpc/h. The correlation function can be well fitted by an empirical relation of the form C_L(r) propto. exp(-[r/r_0]^beta).