Large‐scale asymmetry in galaxy spin directions: Analysis of galaxies with spectra in <scp>DES</scp>, <scp>SDSS</scp>, and <scp>DESI</scp> Legacy Survey

Shamir, Lior

doi:10.1002/asna.20220010

Cited by 7 publications

(25 citation statements)

References 182 publications

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“…Therefore, limiting the redshift to 0.1 is expected to show low statistical significance. The low statistical significance shown in (Iye et al, 2021) agrees with the random distribution in that redshift range as shown in (Shamir, 2020c(Shamir, , 2022c.…”

Section: Iye Et Al (2021) Performed Experiments With Two Datasetssupporting

confidence: 78%

“…Also, an experiment reported in (Shamir, 2020c) used galaxies limited to z < 0.15, and showed that the statistical significance of the dipole axis was below 2σ. A similar experiment (Shamir, 2022c) also showed that the dipole axis is not statistically significant in the lower redshift ranges, including 0 < z < 0.1. Therefore, limiting the redshift to 0.1 is expected to show low statistical significance.…”

Section: Iye Et Al (2021) Performed Experiments With Two Datasetsmentioning

confidence: 80%

“…A correlation was also identified between the cosmic initial conditions and spin directions of galaxies (Motloch et al, 2021). Experiments showed that the strength of the asymmetry is not necessarily affected when limiting the size of the galaxies (Shamir, 2020c), but showed inconclusive evidence of 1.1σ that the asymmetry increases as the density of the galaxies gets larger (Shamir, 2022c).…”

Section: Introductionmentioning

confidence: 93%

“…An analysis with ∼ 1.3•10 6 galaxies allowed to show a dipole axis alignment without the need to fit it in a certain statistical model (Shamir, 2022a). The parity violation seems to become stronger as the redshift increases (Shamir, 2020c(Shamir, , 2022c. Other studies include a smaller number of galaxies to show links between the spin directions of neighboring galaxies (Mai et al, 2022), including galaxies that are too far from each other to have gravitational interactions (Lee et al, 2019b).…”

Section: Introductionmentioning

confidence: 99%

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Using 3D and 2D analysis for analyzing large-scale asymmetry in galaxy spin directions

Shamir

2022

Publications of the Astronomical Society of Japan

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The nature of galaxy spin is still not fully known. Iye, Yagi, and Fukumoto (2021, AJ, 907, 123) 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 0.29σ. However, to show random distribution, two decisions were made, each of which 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 a low statistical signal under these conditions is expected. When using the exact same data without limiting to zphot < 0.1 and without using the photometric redshift, the distribution of the spin directions in that dataset shows a statistical signal of >2σ. 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 suggests that large-scale asymmetry between the number of clockwise and counterclockwise galaxies cannot be ruled out.

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Section: Iye Et Al (2021) Performed Experiments With Two Datasetssupporting

confidence: 78%

Section: Iye Et Al (2021) Performed Experiments With Two Datasetsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Using 3D and 2D analysis for analyzing large-scale asymmetry in galaxy spin directions

Shamir

2022

Publications of the Astronomical Society of Japan

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“…The ability to annotate galaxies automatically allowed analyses based on far larger catalogs that are not subjected to the bias of the human perception. Such analysis showed clear statistical signal of non-random distribution and dipole axis alignment in data taken from SDSS [501], Pan-STARRS [502], Hubble Space Telescope [503], DES [504], and DESI Legacy Survey [505]; all data sets show very similar profiles of asymmetry, and dipole axes well-within 1 σ statistical error from each other [506]. The axes were observed in data collected from telescopes located in the Northern hemisphere [502], and nearly identical patterns were observed when using data collected by telescopes in the Southern [505] hemispheres.…”

Section: Dipole In the Distribution Of Galaxy Spin Directionsmentioning

confidence: 88%

Is the observable Universe consistent with the cosmological principle?

Aluri

Cea

Chingangbam

et al. 2023

Class. Quantum Grav.

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The Cosmological Principle (CP) -- the notion that the Universe is spatially isotropic and homogeneous on large scales -- underlies a century of progress in cosmology. It is conventionally formulated through the Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) cosmologies as the spacetime metric, and culminates in the successful and highly predictive $\Lambda$-Cold-Dark-Matter ($\Lambda$CDM) model. Yet, tensions have emerged within the $\Lambda$CDM model, most notably a statistically significant discrepancy in the value of the Hubble constant, $H_0$. Since the notion of cosmic expansion determined by a single parameter is intimately tied to the CP, implications of the $H_0$ tension may extend beyond $\Lambda$CDM to the CP itself. This review surveys current observational hints for deviations from the expectations of the CP, highlighting synergies and disagreements that warrant further study. Setting aside the debate about individual large structures, potential deviations from the CP include variations of cosmological parameters on the sky, discrepancies in the cosmic dipoles, and mysterious alignments in quasar polarizations and galaxy spins. While it is possible that a host of observational systematics are impacting results, it is equally plausible that precision cosmology may have outgrown the FLRW paradigm, an extremely pragmatic but non-fundamental symmetry assumption.

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Galaxy spin direction asymmetry in JWST deep fields

Shamir

2024

Publ. Astron. Soc. Aust.

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The unprecedented imaging power of JWST provides new abilities to observe the shapes of objects in the early Universe in a way that has not been possible before. Recently, JWST acquired a deep field image inside the same field imaged in the past as the HST Ultra Deep Field. Computer-based quantitative analysis of spiral galaxies in that field shows that among 34 galaxies for which their rotation of direction can be determined by the shapes of the arms, 24 rotate clockwise, and just 10 rotate counterclockwise. The one-tailed binomial distribution probability to have asymmetry equal or stronger than the observed asymmetry by chance is ∼0.012. While the analysis is limited by the small size of the data, the observed asymmetry is aligned with all relevant previous large-scale analyses from all premier digital sky surveys, all show a higher number of galaxies rotating clockwise in that part of the sky, and the magnitude of the asymmetry increases as the redshift gets higher. This paper also provides data and analysis to reproduce previous experiments suggesting that the distribution of galaxy rotation in the Universe is random, to show that the exact same data used in these studies in fact show non-random distribution, and in excellent agreement with the results shown here. These findings reinforce consideration of the possibility that the directions of rotation of spiral galaxies as observed from Earth are not necessarily randomly distributed. The explanation can be related to the large-scale structure of the Universe, but can also be related to a possible anomaly in the physics of galaxy rotation.

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Large‐scale asymmetry in galaxy spin directions: Analysis of galaxies with spectra in DES, SDSS, and DESI Legacy Survey

Cited by 7 publications

References 182 publications

Using 3D and 2D analysis for analyzing large-scale asymmetry in galaxy spin directions

Using 3D and 2D analysis for analyzing large-scale asymmetry in galaxy spin directions

Is the observable Universe consistent with the cosmological principle?

Galaxy spin direction asymmetry in JWST deep fields

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