Space

April 4, 2014

NASA Hubble team finds monster ‘El Gordo’ galaxy cluster bigger than thought

This is a Hubble image of the most massive cluster of galaxies ever seen to exist when the universe was just half its current age of 13.8 billion years. The cluster contains several hundred galaxies.

NASA’s Hubble Space Telescope has weighed the largest known galaxy cluster in the distant universe, catalogued as ACT-CL J0102-4915, and found it definitely lives up to its nickname – El Gordo (Spanish for “the fat one”).

By measuring how much the cluster’s gravity warps images of galaxies in the distant background, a team of astronomers has calculated the cluster’s mass to be as much as 3 million billion times the mass of our sun. Hubble data show the galaxy cluster, which is 9.7 billion light-years away from Earth, is roughly 43 percent more massive than earlier estimates.

The team used Hubble to measure how strongly the mass of the cluster warped space. Hubble’s high resolution allowed measurements of so-called “weak lensing,” where the cluster’s immense gravity subtly distorts space like a funhouse mirror and warps images of background galaxies. The greater the warping, the more mass is locked up in the cluster.

“What I did is basically look at the shapes of the background galaxies that are farther away than the cluster itself,” explained lead author James Jee of the University of California at Davis. “It’s given us an even stronger probability that this is really an amazing system very early in the universe.” said

A fraction of this mass is locked up in several hundred galaxies that inhabit the cluster and a larger fraction is in hot gas that fills the entire volume of the cluster. The rest is tied up in dark matter, an invisible form of matter that makes up the bulk of the mass of the universe.

Though equally massive galaxy clusters are found in the nearby part of the universe, such as the Bullet cluster, nothing like this has ever been discovered to exist so far back in time, when the universe was roughly half its current estimated age of 13.8 billion years. The team suspects such monster galaxy clusters are rare in the early universe, based on current cosmological models.

The immense size of El Gordo was first reported in January 2012. Astronomers estimated its mass based on observations made by NASA’s Chandra X-ray Observatory, and galaxy velocities measured by the European Southern Observatory’s Very Large Telescope array in Paranal, Chile. They were able to put together estimates of the cluster’s mass based on the motions of the galaxies moving inside the cluster and the temperatures of the hot gas between those galaxies.

The challenge was that El Gordo looked as if it might have been the result of a titanic collision between a pair of galaxy clusters — an event researchers describe as two cosmic cannonballs hitting each other.

“We wondered what happens when you catch a cluster in the midst of a major merger and how the merger process influences both the X-ray gas and the motion of the galaxies,” explained John Hughes of Rutgers University. “So, the bottom line is because of the complicated merger state, it left some questions about the reliability of the mass estimates we were making.”

That is where the Hubble data came in, according to Felipe Menanteau of the University of Illinois at Urbana-Champaign.

“We were in dire need for an independent and more robust mass estimate given how extreme this cluster is and how rare its existence is in the current cosmological model. There was all this kinematic energy that was unaccounted for and could potentially suggest that we were actually underestimating the mass,” Menanteau said.

The expectation of “unaccounted energy” comes from the fact the merger of galaxy clusters is occurring tangentially to the observers’ line-of-sight. This means they are potentially missing a good fraction of the kinetic energy of the merger because their spectroscopic measurements only track the radial speeds of the galaxies.

The team’s next step with Hubble will be to compile an image of the cluster. Because El Gordo does not fit into Hubble’s field of view, the team will capture images of sections of the galaxy cluster and piece them together into a mosaic.

Researchers say it is like observing a giant from the side.

“We can tell it’s a pretty big El Gordo, but we don’t know what kind of legs he has, so we need to have a larger field of view to get the complete picture of the giant,” said Menanteau.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.




All of this week's top headlines to your email every Friday.


 
 

 

Headlines June 29, 2015

News: SpaceX Falcon 9 explodes moments after launch – A SpaceX rocket carrying supplies to the International Space Station blew up June 28 shortly after liftoff.   Business: How serious a setback is SpaceX rocket explosion? – Elon Musk had never come face to face with that rule before — at least not in space travel —...
 
 

News Briefs June 29, 2015

Iraqi pilot in Arizona plane crash found dead Officials say the body of an Iraqi pilot who had been training in the United States and crashed in southern Arizona has been located. Iraq’s Defense Ministry said June 26 that search teams found the body of Brig. Gen. Rasid Mohammed Sadeeq at the crash site five...
 
 
Huntington Ingalls Industries photograph

PCU John Warner delivered to Navy

Huntington Ingalls Industries photograph A dolphin jumps in front of the Virginia-class attack submarine Pre-Commissioning Unit (PCU) John Warner (SSN 785) as the boat conducts sea trials in the Atlantic Ocean. The U.S. Navy ac...
 

 
navair-helo

HX-21 completes first flight with developmental electronic warfare pod

On June 8, 2015, a UH-1Y from Air Test and Evaluation Squadron (HX) 21 completed the first test flight with a developmental electronic warfare pod.  The pod would represent a new tactical capability for U.S. Marine Corps rotar...
 
 

Northrop, Navy celebrate legacy of EA-6B Prowler

Northrop Grumman photograph by Edgar Mills The U.S. Navy’s last operational EA-6B Prowler, designed and built by Northrop Grumman, lifts off from Naval Air Station Whidbey Island, Wash. in a ceremonial fly-away June 27 from its long time operational base. The Navy is retiring the Prowler after nearly 45 years of service.   The U.S....
 
 
Air Force photograph by Capt. Tania Bryan

NORTHERN EDGE provides environment for testing new capabilities

Air Force photograph by Capt. Tania Bryan Aircraft from test and evaluation squadrons across the Air Force line up on the Joint Base Elmendorf-Richardson flightline. Northern Edge is Alaska’s premier joint training exercise d...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>