Evidence for the alignment of quasar radio polarizations with large quasar group axes

TL;DR

This study provides evidence that quasar radio polarization vectors are aligned with large quasar group axes, indicating a correlation between quasar spin axes and large-scale cosmic structures, consistent across optical and radio observations.

Contribution

It demonstrates a large-scale correlation between quasar spin axes and LQG axes using radio polarization data, extending previous optical findings and analyzing a large SDSS-based sample.

Findings

Quasar spin axes tend to align with LQG axes in groups with ≥20 members.

In smaller groups, quasar spin axes tend to be perpendicular to LQG axes.

No correlation is observed in groups with fewer than 10 members.

Abstract

Recently, evidence has been presented for the polarization vectors from quasars to preferentially align with the axes of the large quasar groups (LQG) to which they belong. This report was based on observations made at optical wavelengths for two large quasar groups at redshift $\sim 1.3$. The correlation suggests that the spin axes of quasars preferentially align with their surrounding large-scale structure that is assumed to be traced by the LQGs. Here, we consider a large sample of LQGs built from the Sloan Digital Sky Survey DR7 quasar catalogue in the redshift range $1.0-1.8$. For quasars embedded in this sample, we collected radio polarization measurements with the goal to study possible correlations between quasar polarization vectors and the major axis of their host LQGs. Assuming the radio polarization vector is perpendicular to the quasar spin axis, we found that the quasar spin axis is preferentially parallel to the LQG major axis inside LQGs that have at least $20$ members. This result independently supports the observations at optical wavelengths. We additionally found that when the richness of an LQG decreases, the quasar spin axis becomes preferentially perpendicular to the LQG major axis and that no correlation is detected for quasar groups with fewer than $10$ members.