Intrinsic Alignments and Spin Correlations of [OII] Emitters at $z=1.2$ and $z=1.5$ from HSC Narrow-band Survey

TL;DR

This study investigates intrinsic galaxy alignments and spin correlations of [OII] emitters at redshifts 1.2 and 1.5 using HSC data, finding weak signals that inform galaxy formation and weak lensing systematics.

Contribution

First measurement of galaxy-ellipticity and spin correlations for high-redshift star-forming galaxies using narrow-band survey data.

Findings

No significant alignment signals above 1 h^{-1} Mpc.

Weak spin-filament correlation at z=1.47 below 1 h^{-1} Mpc.

Alignment amplitude parameters are consistent with zero within errors.

Abstract

Galaxies are known to be aligned toward specific directions within the large-scale structure. Such alignment signals become important for controlling the systematics of weak lensing surveys and for constraining galaxy formation and evolution scenarios. We measure the galaxy-ellipticity and ellipticity-ellipticity correlation functions for blue star-forming galaxies at $z=1.19$ and $z=1.47$ that are selected by detecting [OII] emission lines in narrow-band filters of the Hyper Suprime-Cam on the Subaru Telescope. Assuming that disk galaxies are thin and rotation-supported, we also measure the spin correlation function by estimating spin directions with ellipticities and position angles. Above $1 \; h^{-1}{\rm Mpc}$, we do not find significant signals for galaxy-ellipticity, ellipticity-ellipticity, or spin correlations at both redshifts. Below $1 \; h^{-1}{\rm Mpc}$, a weak deviation from zero is seen at $z=1.47$, implying weak spin-filament correlations, but it is not verified by the direct comparison between angles of spins and filaments. The linear alignment model fit yields the amplitude parameter $A_{\rm NLA}=1.38\pm2.32$ at $z=1.19$ and $0.45\pm2.09$ at $z=1.47$ ($95\%$ confidence levels). We discuss various observational and physical origins that affect the search for alignments of disk galaxies at high redshifts.