Most distant massive galaxy cluster identified





Michael McDonald, assistant professor of physics and a member of MIT's Kavli Center for Astrophysics and Space Research, says such a collision may explain how IDCS 1426 formed so quickly in the early universe, at a time when individual galaxies were only beginning to take shape.

"In the grand scheme of things, galaxies probably didn't start forming until the universe was relatively cool, and yet this thing has popped up very shortly after that," McDonald says. "Our guess is that another similarly massive cluster came in and sort of wrecked the place up a bit. That would explain why this is so massive and growing so quickly. It's the first one to the gate, basically."

McDonald and his colleagues presented their results this week at the 227th American Astronomical Society meeting in Kissimmee, Florida. Their findings will also be published in The Astrophysical Journal.

"Cities in space"


"They are sort of like cities in space, where all these galaxies live very closely together," McDonald says. "In the nearby universe, if you look at one galaxy cluster, you've basically seen them all — they all look pretty uniform. The further back you look, the more different they start to appear."


In 2012, scientists using NASA's Spitzer Space Telescope first detected signs of IDCS 1426 and made some initial estimates of its mass.

"We had some sense of how massive and distant it was, but we weren't fully convinced," McDonald says. "These new results are the nail in the coffin that proves that it is what we initially thought."

"Tip of the iceberg"

To get a more precise estimate of the galaxy cluster's mass, McDonald and his colleagues used data from several of NASA's Great Observatories: the Hubble Space Telescope, the Keck Observatory, and the Chandra X-ray Observatory.

"We were basically using three completely different methods to weigh this cluster," McDonald explains.





"This cluster is sort of like a construction site — it's messy, loud, and dirty, and there's a lot that's incomplete," McDonald says. "By seeing that incompleteness, we can get a sense for how [clusters] grow. So far, we've confirmed about a dozen or so galaxies, but we're just seeing the tip of the iceberg, really."


"People had kind of put away this idea of finding clusters in the optical and infrared, in favor of X-ray and radio signatures," McDonald says. "We're now re-emerging and saying it's actually a fantastic way of finding clusters. It suggests that maybe we need to branch out a little more in how we find these things."


This research was funded, in part, by NASA.

Additional background

Archive: Why isn't the universe as bright as it should be?

Archive: Most massive and luminous galaxy cluster identified

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