Prospects for detection and application of the alignment of galaxies with the large-scale velocity field

TL;DR

This paper predicts the detectability of galaxy shape and large-scale velocity field correlations using upcoming surveys, highlighting its potential to improve understanding of intrinsic alignments and large-scale structure.

Contribution

It introduces a Fisher forecast for the velocity-shape correlation detectability and discusses its applications in mitigating intrinsic alignment effects and studying their scale dependence.

Findings

Velocity-shape correlation signal-to-noise ratio is 7.4.

Galaxy density-shape correlation has a higher SNR of 44.

Potential to improve intrinsic alignment mitigation and scale dependence analysis.

Abstract

Studies of intrinsic alignment effects mostly focus on the correlations between shapes of galaxies with each other, or with the underlying density field of the large scale structure of the universe. Lately, the correlation between shapes of galaxies and the large-scale velocity field has been proposed as an additional probe of the large scale structure. We use a Fisher forecast to make a prediction for the detectability of this velocity-shape correlation with a combination of redshifts and shapes from the 4MOST+LSST surveys, and radial velocity reconstruction from the Simons Observatory. The signal-to-noise ratio for the velocity-shape (dipole) correlation is 7.4, relative to 44 for the galaxy density-shape (monopole) correlation and for a maximum wavenumber of $0.2\: \mathrm{Mpc^{-1}}$. Encouraged by these predictions, we discuss two possible applications for the velocity-shape correlation. Measuring the velocity-shape correlation could improve the mitigation of selection effects induced by intrinsic alignments on galaxy clustering. We also find that velocity-shape measurements could potentially aid in determining the scale-dependence of intrinsic alignments when multiple shape measurements of the same galaxies are provided.