Astronomers from the Leibniz Astrophysical Institute Potsdam (Germany), in cooperation with scientists from China and Estonia, have discovered for the first time the rotation of the largest cosmological structures in the universe. The discovery is reported in an article.
Although cosmic structures range in scale from dwarf galaxies to giant superclusters, the generation of angular momentum among the largest of them has been poorly studied. In a new paper, scientists investigated whether galactic filaments (filaments), the largest observable structures made up of galaxies in the universe, averaging 160-260 million light-years in length, could rotate. The filaments connect clusters of galaxies to each other and are separated by voids, giant voids. Galaxies inside the threads tend toward the clusters at the ends of the threads, attracted by a large gravitational mass.
Researchers analyzed the motion of galaxies in thousands of filaments using the Sloan Digital Sky Survey (SDSS), which provides scientists with data on millions of galaxies, their spectral images and redshift magnitudes. Astronomers measured the speed of those galaxies that move perpendicular to the axis of the filament by their redshift and blueshift, resulting from the Doppler effect (with redshift the object is moving away from the observer, with blueshift it is moving closer). It turned out that galaxies exhibit spiral motion, i.e. they rotate around the axis while moving along the filament. This makes the filaments the largest objects with angular momentum.
Galactic filament rotation is clearly detected when viewed from the side of the filament, with the more massive the halo at the ends of the filaments, the greater the rotation detected. The mechanism of twisting of the filaments is still a mystery.
It is known that no rotation existed in the early Universe. According to the standard model, the formation of regions of excess density arises due to gravitational instability. Matter begins to flow toward such regions, forming large-scale cosmological structures, but such flows were vortex-free. In other words, rotation should arise later, during formation of the structures themselves.