Detection of a Dipole in the Handedness of Spiral Galaxies with Redshifts z ~ 0.04

TL;DR

This study detects a significant dipole asymmetry in the handedness of spiral galaxies at redshifts around 0.04, suggesting a possible large-scale parity violation or preferred cosmic axis.

Contribution

It provides the first unbinned analysis of galaxy spin handedness revealing a dipole asymmetry without prior axis assumptions, linking galaxy spins to cosmic anisotropies.

Findings

Dipole asymmetry in galaxy handedness with 7.9 x 10^-4 probability of chance occurrence

Dipole axis roughly aligned with the Galactic plane and CMB anomalies

Spin correlation extends up to ~210 Mpc/h, smaller at <20 Mpc/h

Abstract

A preference for spiral galaxies in one sector of the sky to be left-handed or right-handed spirals would indicate a parity violating asymmetry in the overall universe and a preferred axis. This study uses 15158 spiral galaxies with redshifts <0.085 from the Sloan Digital Sky Survey. An unbinned analysis for a dipole component that made no prior assumptions for the dipole axis gives a dipole asymmetry of -0.0408\pm0.011 with a probability of occurring by chance of 7.9 x 10-4. A similar asymmetry is seen in the Southern Galaxy spin catalog of Iye and Sugai. The axis of the dipole asymmetry lies at approx. (l, b) =(52{\deg}, 68.5{\deg}), roughly along that of our Galaxy and close to alignments observed in the WMAP cosmic microwave background distributions. The observed spin correlation extends out to separations ~210 Mpc/h, while spirals with separations < 20 Mpc/h have smaller spin correlations.