Detection of cosmic effect may bring universe’s formation into sharper focus


(Image courtesy of Sundeep Das, University of California-Berkeley)

The first observation of a cosmic effect theorized 40 years ago could provide astronomers with a more precise tool for understanding the forces behind the universe’s formation and growth, including the enigmatic phenomena of dark energy and dark matter.

A large research team from two major astronomy surveys reported in July 2012 that scientists detected the movement of distant galaxy clusters via the kinematic Sunyaev-Zel’dovich (kSZ) effect, which has never before been seen. The work, which appeared in the July 23 issue of the journal Physical Review Letters, was initiated at Princeton University by lead author Nick Hand, Class of 2011, as part of his senior thesis.

Proposed in 1972 by Russian physicists Rashid Sunyaev and Yakov Zel’dovich, the kSZ effect results when the hot gas in galaxy clusters distorts the cosmic microwave background radiation — which is the glow of the heat left over from the Big Bang — that fills our universe. Radiation passing through a galaxy cluster moving toward Earth appears hotter by a few millionths of a degree, while radiation passing through a cluster moving away appears slightly
cooler (see illustration).

Now that it has been detected, the kSZ effect could prove to be an exceptional tool for measuring the velocity of objects in the distant universe, the researchers report. It could provide insight into the strength of the gravitational forces pulling on galaxy clusters and other bodies and on the still-hypothetical dark energy and dark matter in the universe. The effect also can be used to trace the location of atoms in the nearby universe, which can reveal how galaxies form.

“One of the main advantages of the kSZ effect is that its magnitude is independent of a galaxy cluster’s distance from us, so we can measure the velocity of an object’s motion toward or away from Earth at much larger distances than we can now,” said Hand, who conducted the work with his senior thesis adviser David Spergel, the Charles A. Young Professor of Astronomy on the Class of 1897 Foundation and chair of astrophysical sciences at Princeton.

The paper featured 58 collaborators from the Atacama Cosmology Telescope, which is supported primarily by the National Science Foundation (NSF), and the Baryon Oscillation Spectroscopic Survey (BOSS) project. BOSS is a part of the Sloan Digital Sky Survey III, which is supported by the NSF, the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science and participating institutions.