Handedness asymmetry of spiral galaxies with z<0.3 shows cosmic parity violation and a dipole axis

Abstract

A dataset of 126,501 spiral galaxies taken from Sloan Digital Sky Survey was used to analyze the largescale galaxy handedness in different regions of the local universe. The analysis was automated by using a transformation of the galaxy images to their radial intensity plots, which allows automatic analysis of the galaxy spin and can therefore be used to analyze a large galaxy dataset. The results show that the local universe (z<0.3) is not isotropic in terms of galaxy spin, with probability P <∼ 5.8 · 10−6 of such asymmetry to occur by chance. The handedness asymmetries exhibit an approximate cosine dependence, and the most likely dipole axis was found at RA=132o , DEC=32 o with 1σ error range of 107 o to 179 o for the RA. The probability of such axis to occur by chance is P < 1.95 · 10 −5 . The amplitude of the handedness asymmetry reported in this paper is generally in agreement with Longo, but the statistical significance is improved by a factor of 40, and the direction of the axis disagrees somewhat.

Photometric Asymmetry Between Clockwise and Counterclockwise Spiral Galaxies in SDSS

“…These results are in agreement with previous studies using manually classified galaxies (Shamir 2016(Shamir , 2012Hoehn & Shamir 2014), but other studies using a smaller number of galaxies (Shamir 2016) or manually classified galaxies (Land et al 2008) do not show statistically significant preference for a certain handedness. The differences between some of the measurements are statistically significant, and were deduced using a fully automatic process, leading to the conclusion that the SDSS photometric pipeline is sen-8 Shamir sitive to the handedness of the galaxy, and provided different photometric measurements for galaxies of different handedness.…”

“…Land et al (2008) used a large dataset of galaxies annotated by crowdsourcing, showing that after correcting for the substantial human bias the number of galaxies with clockwise handedness was higher than the number of counterclockwise galaxies, but the difference was not statistically significant (Land et al 2008). A more recent analysis using 13,440 automatically classified galaxies (Shamir 2016) showed a higher number of galaxies with clockwise handedness compared to galaxies with counterclockwise handedness, which is also in 2 Shamir agreement with the higher number of Galaxy Zoo (Lintott et al 2011) clockwise galaxies observed in (Shamir 2012). On the other hand, the dataset of 10,281 galaxies used in (Shamir 2016) showed no statistically significant preference (Shamir 2016).…”

“…Related observations have also been related to large-scale asymmetry in the local universe (Longo 2011;Shamir 2012;Gullu & Tekin 2013). While that explanation conflicts with some current cosmological assumptions, current cosmological models might not be complete (Kroupa 2012;Kragh 2013), and the cosmological principle is challenged by the observation of possible large structures (Clowes et al 2013;Horvath et al 2013), exceeding the size limit of structures that do not violate the homogeneity aspect of the cosmological principle (Yadav et al 2010).…”

“…The probability to have 82,244 or more successes is P 5 · 10 −7 . The higher number of clockwise galaxies is aligned with the ratio between clockwise and counterclockwise galaxies in datasets of manually classified spiral galaxies (Shamir 2016(Shamir , 2012Hoehn & Shamir 2014). Other experiments using automatic (Shamir 2016) and manually (Land et al 2008) classified galaxies showed a higher number of galaxies with clockwise handedness, although the difference was not statistically significant.…”

“…Linear regression is applied across the vertical lines of the radial intensity plot for each group of peaks, and the sign of the slopes reflect the direction of the arm, therefore determining the handedness of the galaxy. The algorithm is described in details and numerous examples in (Shamir 2011b;Hoehn & Shamir 2014;Shamir 2012), and the process of galaxy classification is described in (Shamir 2016).…”