Asymmetry in galaxy spin directions: a fully reproducible experiment using HSC data

TL;DR

This study analyzes galaxy spin direction asymmetry using HSC DR3 data, revealing a significant dipole pattern that correlates with redshift and aligns with prior observations, emphasizing the importance of reproducibility in scientific research.

Contribution

It provides a fully reproducible experiment with data, code, and protocol to analyze galaxy spin asymmetry, confirming previous findings and addressing reproducibility issues.

Findings

Galaxies rotating opposite to the Milky Way are more prevalent.

The asymmetry forms a stronger dipole axis at higher redshifts.

Results align with observations from other major sky surveys.

Abstract

The asymmetry in the large-scale distribution of the directions towards spiral galaxies rotate has been observed by multiple telescopes, all show a consistent asymmetry in the distribution of galaxy spin directions as observed from Earth. Here, galaxies with redshift from HSC DR3 are annotated by their direction of rotation, and their distribution is analyzed. The results show that galaxies that rotate in the opposite direction relative to the Milky Way as observed from Earth are significantly more prevalent compared to galaxies that rotate in the same direction relative to the Milky Way. The asymmetry also forms a dipole axis that becomes stronger when the redshift gets higher. These results are aligned with observations from virtually all premier digital sky surveys, as well as space telescopes such as HST and JWST. That shows that the distribution of galaxy spin directions as observed from Earth is not symmetric, and has a possible link to the rotational velocity of the Milky Way. The experiment is provided with data, code, and a full protocol that allows to easily reproduce the results in a transparent manner. That practice is used to overcome the ``reproducibility crisis" in science.