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A statistical search for correlations of rotational spin angular momentum between galaxies

by Hajime Sugai, Masanori Iye
Monthly Notices of the Royal Astronomical Society ()


We report the methods and results of statistical analyses used to search for spatial correlation in the distribution of spin angular momentum of galaxies. A compilation of signs of the line-of-sight component of the spin angular momentum of 9825 spirals in the whole sky, as determined from the spiral winding sense, S-wise or Z-wise, was used in the present analyses for the first time. The expected distribution of spin vectors of galaxies shows markedly different trends according to the galaxy formation scenarios. If galaxy spins were generated according to the primordial whirl scenario, then a dipole segregation of S/Z spins would be observed in their global distribution in the sky, or a strong bias in either the S or Z spin would be seen in a face-on cluster/group of galaxies. A quadrupole distribution of S/Z spins might be observed if the primary process was the generation of spins due to the pancake shock scenario or the explosion scenario. On the other hand, if the galaxy spins were produced by the tidal spin-up process, there would be no global anisotropy unless galaxy-cluster tidal interaction rather than galaxy-galaxy tidal interaction were the primary process. The present multipole analyses have shown no significant dipole or quadrupole anisotropy in the spin vector distribution for the whole sample of galaxies or for Local Supercluster member galaxies. As for the correlation at smaller scales, we looked for but found no departure from the random binomial distribution of S- and Z-wise galaxies in either the sample of 90 groups of galaxies or the sample of 5740 nearest neighbouring pairs of galaxies. These negative results are compatible with the pancake shock scenario, the explosion scenario and the tidal spin-up theory, but not with the primordial whirl scenario.

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