Asymmetry in galaxy spin directions -- analysis of data from DES and comparison to four other sky surveys

TL;DR

This study analyzes galaxy spin directions from DES and other sky surveys, revealing a consistent large-scale dipole axis that challenges the assumption of random galaxy orientations, with implications for cosmology.

Contribution

The paper provides the first large-scale analysis of galaxy spin directions across multiple surveys, identifying a persistent dipole axis and discussing potential errors and implications.

Findings

All surveys show dipole axes within 52° of each other.

Galaxy spin directions are not randomly distributed at large scales.

Results are consistent across different telescopes and data annotation methods.

Abstract

The paper shows an analysis of the large-scale distribution of galaxy spin directions of 739,286 galaxies imaged by DES. The distribution of the spin directions of the galaxies exhibits a large-scale dipole axis. Comparison of the location of the dipole axis to a similar analysis with data from SDSS, Pan-STARRS, and DESI Legacy Survey shows that all sky surveys exhibit dipole axes within 52$^o$ or less from each other, well within 1$\sigma$ error. While non-random distribution is unexpected, the findings are consistent across all sky surveys, regardless of the telescope or whether the data were annotated manually or automatically. Possible errors that can lead to the observation are discussed. The paper also discusses previous studies showing opposite conclusions,and analyzes the decisions that led to these results. Although the observation is provocative, and further research will be required, the existing evidence justifies to consider the contention that galaxy spin directions as observed from Earth are not necessarily randomly distributed. Possible explanations can be related to mature cosmological theories, but also to the internal structure of galaxies.