MIT astronomers discover previously overlooked galaxy clusters

Astronomers from MIT have discovered new galaxy clusters that previous studies overlooked. The team's research suggests that about one percent of galaxy clusters look atypical and can be misidentified as a single bright galaxy when multiple galaxies exist. Galaxy clusters contain hundreds to thousands of galaxies bound together by gravity.

The MIT research suggests as new cluster-hunting telescopes are launched, astronomers have to pay attention to the new study or risk having an incomplete picture of the universe. Galaxy clusters move through the intracluster medium, described as a hot soup of gas containing more mass than all the stars and all the galaxies with that cluster. The hot gas drives star formation as it cools while emitting x-ray radiation that can be observed with space-based telescopes.

The gas cloud creates an X-ray halo around the galaxy clusters that makes them stand out from more discrete sources of x-rays produced by stars or quasars. The project that discovered the previously overlooked galaxy clusters is called Clusters Hiding in Plain Side or CHiPS survey. Researchers on the project started by choosing potential cluster candidates using decades of experienced observations.

Researcher Taweewat Somboonpanyakul devoted his Ph.D. to the CHiPS survey and used data from ground-based telescopes based in Hawaii and New Mexico along with the Magellan telescopes in Chile to take new images of the remaining sources in the hunt for galaxies that might be a cluster. When a promising candidate was discovered, telescopes like the space-based Chandra X-Ray Observatory and the Hubble Space Telescope were used.

The CHiPS survey is now completed after six years, and the final results include the discovery of three new galaxy clusters. One of those clusters, CHIPS1911+4455, is similar to the Phoenix cluster known for rapid star formation. The discovery is significant because astronomers only know a few other Phoenix-like clusters in existence. CHIPS1911+4455 will be studied more in the future. Overall, the survey found that older x-ray based telescopes missed about one percent of galactic clusters because they looked different than typical clusters.