May 22, 2014
Astronomers Confirm Existence Of Extremely Distant Galaxy Cluster
redOrbit Staff & Wire Reports - Your Universe Online
Many of the oldest and most massive galaxies reside together in enormous structures known as clusters, and now a team of astronomers has confirmed the existence of an unusually distant galaxy cluster – a group of 19 galaxies located at precisely the same distance of 9.9 billion light years.
In research appearing in The Astrophysical Journal, Andrew Newman of the Carnegie Institution for Science and his colleagues explain how they used the Hubble Space Telescope to capture images of the distant cluster JKCS 041. While they have been studying the cluster since 2006, these new observations allowed them to finally confirm its distance.
The study authors took the images of JKCS 041 and used a technique known as spectroscopy to split the starlight from the galaxies into its constituent colors. In a statement, Newman explained that the observations made as part of their research “make this galaxy cluster one of the best-studied structures from the early universe.”
According to the researchers, changes to the structures and star populations of massive galaxies occur as they grow older, but little is known about how they form and evolve. Most of the oldest and most massive galaxies reside in clusters, and these groups are believed to be essential to understanding the lifecycles of old galaxies.
However, very few of these distant structures have actually been discovered to date.
Previously, scientists using the Chandra X-ray Observatory to monitor JKCS 041 discovered X-ray emissions in its vicinity. Those X-rays likely originated from gas contained within the cluster – gas that had been heated to temperatures of approximately 80 million degrees by the massive cluster’s gravity, according to the authors of a companion paper published in Astronomy & Astrophysics.
Today, the oldest and largest galaxies are found in clusters, but astronomers are uncertain as to when and why the massive galaxies stopped forming new stars and became dormant. By seeing the galaxies in JKCS 041 when they were just 10 percent of their current age (roughly 1 billion years old), the researchers found that they had already entered this phase, which is also known as the quiescent phase.
“Because JKCS 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,” explained Newman.
Massive galaxies continue expanding in overall size after becoming quiescent. It is believed that this occurs as galaxies collide with one another, forming a new, larger galaxy. Early clusters are believed to be excellent locations for these collisions to take place. However, Newman and his colleagues discovered that the galaxies in JKCS 041 were actually growing at almost the same rate as non-cluster galaxies.
In addition to Newman, researchers involved in the project included Stefano Andreon and Ginevra Trinchieri of the Osservatorio Astronomico di Brera, Richard Ellis of the California Institute of Technology, Tommaso Treu of the University of California at Santa Barbara, and Anand Raichoor of the Observatorie di Paris.