The JCKS 041 galaxy cluster represents a breakthrough for scientists to study old galaxies and their origins.
Andrew Newman of the Carnegie Institution for Science and his team confirmed the distance of a cluster of 19 galaxies. Their discovery places the galaxy cluster JCKS 041 as an important piece of study on the life cycles of old galaxies.
The JCKS 041 galaxy cluster is the best-studied structure from the early universe, Newman said. The team began studying it in 2006. Using the Hubble Space Telescope, they recently confirmed its distance; the 19 galaxies are 9.9 billion light years away.
The galaxy cluster is unusually distant, and the growth of the galaxies surprised the scientists. The largest and oldest galaxies today are now found in clusters. At some point, these galaxies stop forming new stars; they become dormant. At this stage, they continue to expand in size overall, and galaxies will collide to become larger galaxies, which often happens in clusters. However, the galaxies of JCKS 041 grow at nearly the same rate as non-cluster galaxies. Back when these galaxies were 1 billion years old, 10 percent of their present age, most of them were already dormant. In the Hubble Space Telescope image, the galaxies circled in yellow had entered quiescence while the blue ones continue to form new stars.
Scientists are still trying to determine when and why galaxies become dormant. "Because JCKS 041 is the most-distant known cluster of its size, it gives us a unique opportunity to study these old galaxies in detail and better understand their origins," Newman said.
The Astrophysical Journal has published Newman's team's research on JCKS 041.
Source: Carnegie Institution for Science