Well, it just seems like the universe is getting more crowded every day. New telescopes and technologies are allowing astronomers to discover new astronomical objects all the time, such as these ten new galaxy clusters found by the Atacama Cosmology Telescope (ACT).
The Atacama Desert in Chile is an up-and-coming site for radio and microwave astronomy with the ACT and the Atacama Large Millimeter Array (ALMA), the latter of which is under construction. At an elevation of over 17,000 feet (over 5000 meters), these telescopes get above much of the water vapor in the atmosphere that can absorb or distort the incoming cosmic radiation at these wavelengths.
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These galaxies were not observed directly by the ACT but seen through the Sunyaev-Zel'dovic Effect, or SZE. Essentially, the hot gas molecules in the cluster scatter cosmic microwave background photons up to higher energies. Thus, a "hole" or "shadow" appears in an image made with microwave light.
The SZE is useful for finding clusters at great distances from us, as this sample stretches halfway across the visible universe. Advances in microwave telescopes and cameras have allowed for these surveys of the cosmic microwave background for such galaxy clusters. These clusters can then be studied in their own right, or used as probes for cosmology. The sizes and distribution of galaxy clusters fold into the standard model of cosmology, improving our understanding of dark energy.
23 such clusters were seen by the ACT survey, 10 of which were previously unknown. All of these have been detected by optical telescopes as well, as shown in the image above. With new observatories like ACT and ALMA watching the microwave sky from above the clouds, we're sure to find even more.
Image: Four clusters seen by the ACT with the Sunyaev-Zel'dovic Effect, along with the images of the galaxy clusters from optical telescopes. Credit: top row: Tobias Marriage, Johns Hopkins University, Princeton University. Bottom matrix: Felipe Menanteau, Rutgers University
This research is published in the Astrophysical Journal, and a pre-print is available on arxiv.org.
Tags: Astronomy, Galaxies, Telescopes
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