Large-Scale Photometric Asymmetry in Galaxy Spin Patterns

Shamir, Lior

doi:10.1017/pasa.2017.40

Cited by 22 publications

(48 citation statements)

References 28 publications

(46 reference statements)

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“…The experiments also showed that the photometric differences changed with the direction of observation (Shamir 2017c). These observations are consistent across SDSS and Pan-STARRS, both showing the same profile of the asymmetry (Shamir 2017b). Repeating the same experiment with manually classified galaxies also showed the same results, providing additional evidence that the asymmetry cannot be driven by a computer error (Shamir 2017b).…”

Section: Introductionsupporting

confidence: 69%

“…These observations are consistent across SDSS and Pan-STARRS, both showing the same profile of the asymmetry (Shamir 2017b). Repeating the same experiment with manually classified galaxies also showed the same results, providing additional evidence that the asymmetry cannot be driven by a computer error (Shamir 2017b). The fact that two different telescopes and two different analysis methods provide the same profile of the asymmetry indicates that the asymmetry is not a feature of a specific instrument or photometric pipeline.…”

Section: Introductionsupporting

confidence: 62%

“…A similar experiment was done with Pan-STARRS galaxies, using clockwise and counterclockwise galaxies that were used in a previous experiment (Shamir 2017b). The number of Pan-STARRS galaxies in the same field was 1444 clockwise galaxies and 1438 counterclockwise galaxies, and 21% of them are also present in the SDSS dataset of the same field.…”

Section: Resultsmentioning

confidence: 91%

“…The tables also show the t-test P value of the difference between the means of the magnitude of clockwise and counterclockwise galaxies in all three datasets. The exponential magnitude model was used, but other magnitude models show similar asymmetry (Shamir 2017b). The Student t-test P values are very low in the (120 ∘ , 210 ∘ ) RA range due to the much higher number of galaxies.…”

Section: Discussionmentioning

confidence: 99%

“…The manual annotation of clockwise and counterclockwise galaxies also led to substantial bias, as humans tend to misidentify galaxies that spin counterclockwise as elliptical galaxies (Hayes et al 2016), leading to a systematic bias in the dataset. Analysis (Shamir 2017b) of the average brightness of the clockwise and counterclockwise galaxies classified by Galaxy Zoo as "superclean" (meaning that 95% or more of the voters agreed on the annotation) showed that the difference was in agreement with the direction and magnitude of the difference observed in (Shamir 2017c), but due to the small size of the Galaxy Zoo "superclean" dataset no statistically significant difference or indifference could be determined (Shamir 2017b). Longo (2011) used four undergraduate students to sort SDSS galaxies by their spin pattern, and showed possible differences between the number of clockwise and counterclockwise galaxies in the dataset.…”

Section: Introductionmentioning

confidence: 99%

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Asymmetry between galaxies with different spin patterns: A comparison between COSMOS, SDSS, and Pan-STARRS

Shamir

2020

Open Astronomy

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Previous observations of a large number of galaxies show differences between the photometry of spiral galaxies with clockwise spin patterns and spiral galaxies with counterclockwise spin patterns. In this study the mean magnitude of a large number of clockwise galaxies is compared to the mean magnitude of a large number of counterclockwise galaxies. The observed difference between clockwise and counterclockwise spiral galaxies imaged by the space-based COSMOS survey is compared to the differences between clockwise and counterclockwise galaxies imaged by the Earth-based SDSS and Pan-STARRS around the same field. The annotation of clockwise and counterclockwise galaxies is a fully automatic process that does not involve human intervention, and in all experiments both clockwise and counterclockwise galaxies are separated from the same fields. The comparison shows that the same asymmetry was identified by all three telescopes, providing strong evidence that the rotation direction of a spiral galaxy is linked to its luminosity as measured from Earth. Analysis of the luminosity difference using a large number of galaxies from different parts of the sky shows that the difference between clockwise and counterclockwise galaxies changes with the direction of observation, and oriented around an axis.

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Section: Introductionsupporting

confidence: 69%

Section: Introductionsupporting

confidence: 62%

Section: Resultsmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Asymmetry between galaxies with different spin patterns: A comparison between COSMOS, SDSS, and Pan-STARRS

Shamir

2020

Open Astronomy

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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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Spin parity of spiral galaxies II: a catalogue of 80 k spiral galaxies using big data from the Subaru Hyper Suprime-Cam survey and deep learning

Tadaki

Iye

Fukumoto

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Abstract We report an automated morphological classification of galaxies into S-wise spirals, Z-wise spirals, and non-spirals using big image data taken from Subaru/Hyper Suprime-Cam (HSC) Survey and a convolutional neural network(CNN)-based deep learning technique. The HSC i-band images are about 25 times deeper than those from the Sloan Digital Sky Survey (SDSS) and have a two times higher spatial resolution, allowing us to identify substructures such as spiral arms and bars in galaxies at z > 0.1. We train CNN classifiers by using HSC images of 1447 S-spirals, 1382 Z-spirals, and 51,650 non-spirals. As the number of images in each class is unbalanced, we augment the data of spiral galaxies by horizontal flipping, rotation, and rescaling of images to make the numbers of three classes similar. The trained CNN models correctly classify 97.5% of the validation data, which is not used for training. We apply the CNNs to HSC images of a half million galaxies with an i-band magnitude of i < 20 over an area of 320 deg2. 37,917 S-spirals and 38,718 Z-spirals are identified, indicating no significant difference between the numbers of two classes. Among a total of 76,635 spiral galaxies, 48,576 are located at z > 0.2, where we are hardly able to identify spiral arms in the SDSS images. Our attempt demonstrates that a combination of the HSC big data and CNNs has a large potential to classify various types of morphology such as bars, mergers and strongly-lensed objects.

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Large-Scale Photometric Asymmetry in Galaxy Spin Patterns

Cited by 22 publications

References 28 publications

Asymmetry between galaxies with different spin patterns: A comparison between COSMOS, SDSS, and Pan-STARRS

Asymmetry between galaxies with different spin patterns: A comparison between COSMOS, SDSS, and Pan-STARRS

Galaxy spin direction asymmetry in JWST deep fields

Spin parity of spiral galaxies II: a catalogue of 80 k spiral galaxies using big data from the Subaru Hyper Suprime-Cam survey and deep learning

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