Large-scale asymmetry in galaxy spin directions: evidence from the Southern hemisphere

Abstract

Recent observations using several different telescopes and sky surveys showed patterns of asymmetry in the distribution of galaxies by their spin directions as observed from Earth. These studies were done with data imaged from the Northern hemisphere, showing excellent agreement between different telescopes and different analysis methods. Here, data from the DESI Legacy Survey was used. The initial dataset contains $\sim 2.2\cdot 10^7$ galaxy images, reduced to $\sim 8.1\cdot 10^5$ galaxies annotated by their spin direction using a symmetric algorithm. That makes it not just the first analysis of its kind in which the majority of the galaxies are in the Southern hemisphere, but also by far the largest dataset used for this purpose to date. The results show strong agreement between opposite parts of the sky, such that the asymmetry in one part of the sky is similar to the inverse asymmetry in the corresponding part of the sky in the opposite hemisphere. Fitting the distribution of galaxy spin directions to cosine dependence shows a dipole axis with probability of 4.66$\sigma$. Interestingly, the location of the most likely axis is within close proximity to the CMB Cold Spot. The profile of the distribution is nearly identical to the asymmetry profile of the distribution identified in Pan-STARRS, and it is within 1$\sigma$ difference from the distribution profile in SDSS and HST. All four telescopes show similar large-scale profile of asymmetry.

PASA, accepted

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Cited by in corpus (11)

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• Analysis of spin directions of galaxies in the DESI Legacy Survey
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• Reanalysis of the spin direction distribution of Galaxy Zoo SDSS spiral galaxies
• Using 3D and 2D analysis for analyzing large-scale asymmetry in galaxy spin directions
• Analysis of $\sim 10^6$ spiral galaxies from four telescopes shows large-scale patterns of asymmetry in galaxy spin directions
• Large-scale asymmetry in the distribution of galaxy spin directions -- analysis and reproduction
• Large-scale asymmetry in galaxy spin directions -- analysis of galaxies with spectra in DES, SDSS, and DESI Legacy Survey
• A simple direct empirical observation of systematic bias of the redshift as a distance indicator
• Asymmetry in galaxy spin directions: a fully reproducible experiment using HSC data