No evidence for anisotropy in galaxy spin directions

Abstract

Modern cosmology rests on the cosmological principle, that on large enough scales the Universe is both homogeneous and isotropic. A corollary is that galaxies' spin vectors should be isotropically distributed on the sky. This has been challenged by multiple authors for over a decade, with claims to have detected a statistically significant dipole pattern of spins. We collect all publicly available datasets with spin classifications (binary Z-wise/S-wise), and analyse them for large-angle anisotropies ($\ell \le 2$). We perform each inference in both a Bayesian and frequentist fashion, the former establishing posterior probabilities on the multipole parameters and the latter calculating $p$-values for rejection of the null hypothesis of isotropy (i.e. no power at $\ell >0$). All analysis indicate consistency with isotropy to within $3\sigma$. We similarly identify no evidence for a "hemisphere anisotropy" that neglects the angular dependence of the dipole. We isolate the differences with contrary claims in the ad hoc or biased statistics that they employ. Our code is publicly available.

8 pages, 5 figures; minor revision, matches MNRAS published version

References in corpus (31)

• emcee: The MCMC Hammer
• The Sloan Digital Sky Survey: Technical Summary
• The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
• Is the Observable Universe Consistent with the Cosmological Principle?
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the $L_{\text{X}}-T$ scaling relation
• A Challenge to the Standard Cosmological Model
• Galaxy Zoo: The large-scale spin statistics of spiral galaxies in the Sloan Digital Sky Survey
• Anisotropic Cosmological Constant and the CMB Quadrupole Anomaly
• Detection of a Dipole in the Handedness of Spiral Galaxies with Redshifts z ~ 0.04
• Analyzing the Large-Scale Bulk Flow using CosmicFlows4: Increasing Tension with the Standard Cosmological Model
• Ganalyzer: A tool for automatic galaxy image analysis
• Exploring cosmic homogeneity with the BOSS DR12 galaxy sample
• Scalable Automated Detection of Spiral Galaxy Arm Segments
• Testing the Cosmological Principle with CatWISE Quasars: A Bayesian Analysis of the Number-Count Dipole
• Galaxy Zoo: Chiral correlation function of galaxy spins
• Inference of the cosmic rest-frame from supernovae Ia
• On the nature and correction of the spurious S-wise spiral galaxy winding bias in Galaxy Zoo 1
• Cosmic homogeneity: a spectroscopic and model-independent measurement
• Measuring the scale of cosmic homogeneity with SDSS-IV DR14 quasars
• The dipole anisotropy of AllWISE galaxies
• The multipole expansion of the local expansion rate
• Spin Parity of Spiral Galaxies II: A catalogue of 80k spiral galaxies using big data from the Subaru Hyper Suprime-Cam Survey and deep learning
• Strong Evidence Against a Statistically Isotropic Universe
• A catalog of broad morphology of Pan-STARRS galaxies based on deep learning
• Finding origins of CMB anomalies in the inflationary quantum fluctuations
• Spin Parity of Spiral Galaxies III -- Dipole Analysis of the Distribution of SDSS Spirals with 3D Random Walk Simulations
• 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
• Big Bounce in Dipole Cosmology
• Large-scale asymmetry in the distribution of galaxy spin directions -- analysis and reproduction
• Testing the cosmological principle with the Pantheon+ sample and the region-fitting method

Cited by in corpus (4)

• The distribution of galaxy rotation in JWST Advanced Deep Extragalactic Survey
• Clustering properties of the CatWISE2020 quasar catalogue and their impact on the cosmic dipole anomaly
• Asymmetry in galaxy spin directions: a fully reproducible experiment using HSC data
• Symmetry in Hyper Suprime-Cam galaxy spin directions