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1. Galaxy spin direction distribution in HST and SDSS show similar large-scale asymmetry

   https://doi.org/10.1017/pasa.2020.46  

   Shamir, Lior (January 2020, Publications of the Astronomical Society of Australia)

   null (Ed.)

   Abstract Several recent observations using large data sets of galaxies showed non-random distribution of the spin directions of spiral galaxies, even when the galaxies are too far from each other to have gravitational interaction. Here, a data set of $$\sim8.7\cdot10^3$$ spiral galaxies imaged by Hubble Space Telescope ( HST ) is used to test and profile a possible asymmetry between galaxy spin directions. The asymmetry between galaxies with opposite spin directions is compared to the asymmetry of galaxies from the Sloan Digital Sky Survey. The two data sets contain different galaxies at different redshift ranges, and each data set was annotated using a different annotation method. The results show that both data sets show a similar asymmetry in the COSMOS field, which is covered by both telescopes. Fitting the asymmetry of the galaxies to cosine dependence shows a dipole axis with probabilities of $$\sim2.8\sigma$$ and $$\sim7.38\sigma$$ in HST and SDSS, respectively. The most likely dipole axis identified in the HST galaxies is at $$(\alpha=78^{\rm o},\delta=47^{\rm o})$$ and is well within the $$1\sigma$$ error range compared to the location of the most likely dipole axis in the SDSS galaxies with $z>0.15$ , identified at $$(\alpha=71^{\rm o},\delta=61^{\rm o})$$ . 

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2. Reanalysis of the Spin Direction Distribution of Galaxy Zoo SDSS Spiral Galaxies

   https://doi.org/10.1155/2023/4114004  

   Mcadam, Darius; Shamir, Lior (February 2023, Advances in Astronomy)

   Gaite, Jose (Ed.)

   The distribution of the spin directions of spiral galaxies in the Sloan Digital Sky Survey has been a topic of debate in the past two decades, with conflicting conclusions reported even in cases where the same data were used. Here, we follow one of the previous experiments by applying the SpArcFiRe algorithm to annotate the spin directions in an original dataset of Galaxy Zoo 1. The annotation of the galaxy spin directions is carried out after the first step of selecting the spiral galaxies in three different manners: manual analysis by Galaxy Zoo classifications, by a model-driven computer analysis, and with no selection of spiral galaxies. The results show that when spiral galaxies are selected by Galaxy Zoo volunteers, the distribution of their spin directions as determined by SpArcFiRe is not random, which agrees with previous reports. When selecting the spiral galaxies using a model-driven computer analysis or without selecting the spiral galaxies at all, the distribution is also not random. Simple binomial distribution analysis shows that the probability of the parity violation to occur by chance is lower than 0.01. Fitting the spin directions as observed from the Earth to cosine dependence exhibits a dipole axis with statistical strength of 2.33 σ to 3.97 σ . These experiments show that regardless of the selection mechanism and the analysis method, all experiments show similar conclusions. These results are aligned with previous reports using other methods and telescopes, suggesting that the spin directions of spiral galaxies as observed from the Earth exhibit a dipole axis formed by their spin directions. Possible explanations can be related to the large-scale structure of the universe or to the internal structure of galaxies. The catalogs of annotated galaxies generated as part of this study are available. 

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3. Large‐scale asymmetry between clockwise and counterclockwise galaxies revisited

   https://doi.org/10.1002/asna.202013745  

   Shamir, Lior (April 2020, Astronomische Nachrichten)

   Abstract The ability of digital sky surveys to collect and store very large amounts of data provides completely new ways to study the local universe. Perhaps one of the most provocative observations reported with such tools is the asymmetry between galaxies with clockwise and counterclockwise spin patterns. Here, I use∼1.7 × 10⁵spiral galaxies from Sloan Digital Sky Survey (SDSS) and sort them by their spin patterns (clockwise or counterclockwise) to identify and profile a possible large‐scale pattern of the distribution of galaxy spin patterns as observed from Earth. The analysis shows asymmetry between the number of clockwise and counterclockwise spiral galaxies imaged by SDSS and a dipole axis. These findings largely agree with previous reports using smaller datasets. The probability of the differences between the number of galaxies occurring by chance isp< 4 × 10⁻⁹, and the probability of an asymmetry axis occurring by mere chance isp< 1.4×10⁻⁵. 

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4. New evidence and analysis of cosmological-scale asymmetry in galaxy spin directions

   https://doi.org/10.1007/s12036-022-09809-8  

   Shamir, Lior (January 2022, Journal of astrophysics and astronomy)

   In the past several decades, multiple cosmological theories that are based on the contention that the Universe has a major axis have been proposed. Such theories can be based on the geometry of the Universe, or multiverse theories such as black hole cosmology. The contention of a cosmological-scale axis is supported by certain evidence such as the dipole axis formed by the CMB distribution. Here I study another form of the cosmological-scale axis, based on the distribution of the spin direction of spiral galaxies. Data from four different telescopes are analyzed, showing nearly identical axis profiles when the distribution of the redshifts of the galaxies is similar. 

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5. Using Machine Learning to Profile Asymmetry between Spiral Galaxies with Opposite Spin Directions

   https://doi.org/10.3390/sym14050934  

   Shamir, Lior (April 2022, Symmetry)

   Spiral galaxies can spin clockwise or counterclockwise, and the spin direction of a spiral galaxy is a clear visual characteristic. Since in a sufficiently large universe the Universe is expected to be symmetric, the spin direction of a galaxy is merely the perception of the observer, and therefore, galaxies that spin clockwise are expected to have the same characteristics of galaxies spinning counterclockwise. Here, machine learning is applied to study the possible morphological differences between galaxies that spin in opposite directions. The dataset used in this study is a dataset of 77,840 spiral galaxies classified by their spin direction, as well as a smaller dataset of galaxies classified manually. A machine learning algorithm was applied to classify between images of clockwise galaxies and counterclockwise galaxies. The results show that the classifier was able to predict the spin direction of the galaxy by its image in accuracy higher than mere chance, even when the images in one of the classes were mirrored to create a dataset with consistent spin directions. That suggests that galaxies that seem to spin clockwise to an Earth-based observer are not necessarily fully symmetric to galaxies that spin counterclockwise; while further research is required, these results are aligned with previous observations of differences between galaxies based on their spin directions. 

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