CWRU Astronomers Find Young Galaxy Protoclusters in the Early Universe
Posted on December 18, 2015
A team of CWRU astronomers has recently identified 43 new protoclusters of galaxies, seen as they were 12 billion years in the past, when the Universe was only a few billion years old. These systems bridge the gap between the smooth early universe and the complexity of structure we see today. Barely 300,000 years after the Big Bang, the Universe was hot, dense and very nearly uniform. It had only minute density fluctuations of one part in a hundred thousand. In contrast, at the present time we see galaxies grouped together along filaments and in dense clusters containing thousands of galaxies. The new protoclusters identified by the CWRU team are the uncollapsed, infant counterparts to present day clusters, seen in the distant cosmos when the Universe was young.
CWRU graduate student Jay Franck and Dr. Stacy McGaugh mined through thousands of galaxies with well known distances, searching for overdensities of galaxies in the distant universe. The number, mass, and size of these protoclusters are sensitive to the particular cosmology of our Universe. Varying the amounts of ordinary matter, dark matter and dark energy provide constraints to the observable properties of these systems. Prior to this work, only 20 or so protoclusters had been identified, making this catalog a significant increase in the number of known primordial structures. With this expanded data set, astronomers can try to put another puzzle piece of the Universe in the right place.
A plot of the number of galaxies as a function of redshift along a particular direction in the sky. Spikes in the counts correspond to newly identified protoclusters of galaxies. In this single field (CANDELS GOODS-S), the CWRU team identified 9 protoclusters as galaxy overdensities along the line of sight. At a redshift of 3, light has traveled more than 11 billion years to reach Earth.