Rutgers University | 01 Nov 2010
The Atacama Cosmology Telescope: Physical Properties and Purity of[img3="Four Atacama Cosmology Telescope (ACT) images of cosmic background radiation, top row, with dark blue colors indicating "shadows" cast by galaxy clusters. Below, four optical images of the galaxy clusters, with white contour lines corresponding to the cosmic background radiation intensity levels in the ACT images. (Credit: Top row: Tobias Marriage, Johns Hopkins University, Princeton University. Bottom matrix: Felipe Menanteau, Rutgers University) Hires Image"]http://www.eurekalert.org/multimedia/pu ... 10_web.jpg[/img3]An international team of scientists led by Rutgers University astrophysicists have discovered 10 new massive galaxy clusters from a large, uniform survey of the southern sky. The survey was conducted using a breakthrough technique that detects "shadows" of galaxy clusters on the cosmic microwave background radiation, a relic of the "big bang" that gave birth to the universe.
In a paper published in the Nov. 10 issue of Astrophysical Journal, the Rutgers scientists and collaborators at the Pontifical Catholic University of Chile (PUC) describe their visual telescope observations of these galaxy clusters, which were essential to verify the cosmic shadow sightings. Both observations will help scientists better understand how the universe was born and continues to evolve.
The research began in 2008 with a new radio telescope in the Atacama Desert of Chile – one of the driest places on Earth. The instrument, known as the Atacama Cosmology Telescope (ACT), collects millimeter-length radio waves that reveal images of the otherwise invisible cosmic background radiation. Millimeter waves are easily blocked by water vapor, hence the telescope's home high in the Andes Mountains of northern Chile, where there is barely any atmospheric moisture.
The research began in 2008 with a new radio telescope in the Atacama Desert of Chile – one of the driest places on Earth. The instrument, known as the Atacama Cosmology Telescope (ACT), collects millimeter-length radio waves that reveal images of the otherwise invisible cosmic background radiation. Millimeter waves are easily blocked by water vapor, hence the telescope’s home high in the Andes Mountains of northern Chile, where there is barely any atmospheric moisture.
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Theorists Rashid Sunyaev and Yakov Zel’dovich predicted the shadow phenomenon 40 years ago, now known as the Sunyaev-Zel’dovich effect, or S-Z effect. Shortly thereafter astronomers verified it by observing shadows cast by previously known galaxy clusters. The higher sensitivity and resolution of ACT now makes it practical for astronomers to essentially reverse the procedure – to search the cosmic background radiation for shadows that indicate the presence of unseen clusters.
“The ‘shadows’ that ACT revealed are not shadows in the traditional sense, as they are not caused by the galaxy clusters blocking light from another source,” said Jack Hughes, professor of physics and astronomy at Rutgers. “Rather, the hot gases within the galaxy clusters cause a tiny fraction of the cosmic background radiation to shift to higher energies, which then makes them appear as shadows in one of ACT’s observing bands.”
a Galaxy Cluster Sample Selected via the Sunyaev-Zel'dovich Effect - F Menanteau et al
- Astrophysical Journal 723(2) 1523 (10 Nov 2010) DOI: 10.1088/0004-637X/723/2/1523
arXiv.org > astro-ph > arXiv:1006.5126 > 26 Jun 2010 (v1), 09 Sep 2010 (v2)