In A Galaxy Cluster Far, Far Away

Meet IDCS 1426: the largest, most distant galaxy cluster. UMKC assistant professor Mark Brodwin led the study on details of this star system. This image uses data from the Spitzer, Hubble and Chandra space telescopes.

Mark Brodwin of UMKC leads study that discovers details of largest, most distant star system

The full grandeur of the most distant massive galaxy cluster yet discovered has been revealed using data from three of NASA’s Great Observatories in a new study led by Mark Brodwin of the University of Missouri-Kansas City.

“We are really pushing the boundaries with this discovery,” said Brodwin, assistant professor of physics and astronomy, who presented the findings at a press conference Jan. 7 at the American Astronomical Society meeting in Kissimmee, Florida. “This is one of the earliest massive structures to form in the universe.”




The galaxy cluster is called IDCS J1426.5+3508 — or IDCS 1426 for short — and is located 10 billion light years from Earth.

The mass of IDCS 1426 exceeds that of the previous record holder by over 70 trillion solar masses, and it is substantially farther away, at an additional distance of 360 million light years.

First discovered by the Spitzer Space Telescope in 2012, IDCS 1426 was then observed using the Hubble Space Telescope and the Keck Observatory to determine its distance. Radio observations from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) telescopes indicated it was extremely massive. New data from the Chandra X-ray Observatory confirm the galaxy cluster contains a whopping mass of nearly half a quadrillion times that of the sun.

Galaxy clusters are the largest objects in the universe held together by gravity. Because of their sheer size, scientists believe they take several billion years to form. The distance of IDCS 1426 means astronomers are observing it when the universe was only 3.8 billion years old.

The data from Chandra reveal a bright knot of X-rays near the middle of the cluster, but not exactly at its center. This overdense core has been dislodged from the cluster center, possibly by a merger with another developing cluster, perhaps 500 million years prior. Such a merger would cause the X-ray-emitting hot gas to slosh around like wine in a moving glass.

“Mergers with other groups and clusters of galaxies should have been more common so early in the history of the universe,” said co-author Michael McDonald of the Massachusetts Institute of Technology in Cambridge. “That appears to have played an important part in this young cluster’s rapid formation.”

Aside from this cool core, the hot gas in the rest of the cluster is very smooth and symmetric. This is another indication that IDCS 1426 formed very rapidly. In addition, astronomers do not find any evidence for elements heavier than helium in the hot gas. This suggests that this galaxy cluster might still be in the process of enriching its hot gas with these elements.

“This presence of this massive galaxy cluster in the early universe doesn’t upset our current understanding of cosmology,” said co-author Anthony Gonzalez of the University of Florida in Gainesville. “It does, however, give us more information to work with when we try to refine our models.”

Evidence for other massive galaxy clusters at early times has been found, but none of these are as compelling as IDCS 1426, nor have its combination of mass and distance. The case for IDCS 1426 is extremely strong because it has been made using three independent methods to determine the mass: X-rays from gas trapped in the cluster’s gravity, the imprint of the cluster’s mass on the cosmic microwave background, and distortions in the shapes of galaxies behind the cluster as its gravity bends their light.


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