Dark flow

From SPACEwiki

Dark Flow is a name given to a net motion of galaxy clusters with respect to the cosmic microwave background radiation which was found in a 2008 study. According to standard cosmological models, the motion of galaxy clusters with respect to the cosmic microwave background should be randomly distributed in all directions. However, analyzing the three-year WMAP data using the kinematic Sunyaev-Zel'dovich effect, the authors of the study found evidence of a common motion of at least 600 km/s toward a 20-degree patch of sky between the constellations of Centaurus and Vela.

The authors (A. Kashlinsky, F. Atrio-Barandela, D. Kocevski, and H. Ebeling) suggest that the motion may be a remnant of the influence of no-longer-visible regions of the universe prior to inflation. Telescopes cannot see events earlier than about 380,000 years after the big bang, when the universe became transparent (the Cosmic Microwave Background); this corresponds to the particle horizon at a distance of about 46 billion (4.6×1010) light years. Since the matter causing the net motion in this proposal is outside this range, it would in a certain sense be outside our visible universe; however, it would still be in our past light cone.

The results appear in the October 20, 2008, issue of Astrophysical Journal Letters, which is available online. The authors state that they plan to extend their analysis to additional clusters and the recently released WMAP five-year data.