Large-scale asymmetry in the distribution of galaxy spin directions -- analysis and reproduction

Abstract

Recent independent observations using several different telescope systems an analysis methods have provided evidence of parity violation between the number of galaxies that spin in opposite directions. On the other hand, other studies argued that no parity violation can be identified. This paper provides detailed analysis, statistical inference, and reproduction of previous reports that show no preferred spin direction. Code and data used for the reproduction are publicly available. The results show that the data used in all of these studies agrees with the observation of a preferred direction as observed from Earth. In some of these studies the datasets were too small, or the statistical analysis was incomplete. In other papers the results were impacted by experimental design decisions that lead directly to show non-preferred direction. In some of these cases these decisions are not stated in the papers, but were revealed after further investigation in cases where the reproduction of the work did not match the results reported in the papers. These results show that the data used in all of these previous studies in fact agree with the contention that galaxies as observed from Earth have a preferred spin direction, and the distribution of galaxy spin directions as observed from Earth form a cosmological-scale dipole axis. This study also shows that the reason for the observations is not necessarily an anomaly in the large-scale structure, and can also be related to internal structure of galaxies.