  The nature of galaxy spin is still not fully known. Iye et al (2021) applied
a 3D analysis to a dataset of bright SDSS galaxies that was used in the past
for photometric analysis. They showed that the distribution of spin directions
of spiral galaxies is random, providing a dipole axis with low statistical
significance of 0.29$\sigma$. However, to show random distribution, two
decisions were made, each can lead to random distribution regardless of the
real distribution of the spin direction of galaxies. The first decision was to
limit the dataset arbitrarily to z$<$0.1, which is a redshift range in which
previous literature already showed that random distribution is expected. More
importantly, while the 3D analysis requires the redshift of each galaxy, the
analysis was done with the photometric redshift. If the asymmetry existed, its
signal is expected to be an order of magnitude weaker than the error of the
photometric redshift, and therefore the low statistical signal under these
conditions is expected. When using the exact same data without limiting to
$z_{phot}<0.1$ and without using the photometric redshift, the distribution of
the spin directions in that dataset shows a statistical signal of $>2\sigma$.
Code and data for reproducing the analysis are publicly available. These
results are in agreement with other experiments with SDSS, Pan-STARRS, HST, and
the DESI Legacy Survey. The paper also examines other previous studies that
showed random distribution in galaxy spin directions. While further research
will be required, the current evidence suggest that large-scale asymmetry
between the number of clockwise and counterclockwise galaxies cannot be ruled
out.
