Featured Research

from universities, journals, and other organizations

Monster 'El Gordo' galaxy cluster is bigger than thought

Date:
April 3, 2014
Source:
Space Telescope Science Institute
Summary:
Astronomers have weighed the largest known galaxy cluster in the distant universe and found that it definitely lives up to its nickname: El Gordo (Spanish for "the fat one"). By precisely measuring how much the gravity from the cluster's mass warps images of far-more-distant background galaxies, a team of astronomers has calculated the cluster's mass to be as much as 3 million billion times the mass of our Sun. The Hubble data show that the cluster is roughly 43 percent more massive than earlier estimates based on X-ray and dynamical studies of the unusual cluster.

This is a Hubble Space Telescope image of the most massive cluster of galaxies ever seen to exist when the universe was just half of its current age of 13.8 billion years. The cluster, catalogued as ACT-CL J0102-4915, contains several hundred galaxies swarming around under a collective gravitational pull. The total mass of the cluster, as refined in new Hubble measurements, is estimated to weigh as much as 3 million billion stars like our Sun (about 3,000 times more massive than our own Milky Way galaxy) - though most of the mass is hidden away as dark matter. The location of the dark matter is mapped out in the blue overlay. Because dark matter doesn't emit any radiation, Hubble astronomers instead precisely measure how its gravity warps the images of far background galaxies like a funhouse mirror. This allowed them to come up with a mass estimate for the cluster. The cluster was nicknamed El Gordo (Spanish for "the fat one") in 2012 when X-ray observations (shown in pink) and kinematic studies first suggested it was unusually massive for the time in the early universe when it existed. The Hubble data have confirmed that the cluster is undergoing a violent merger between two smaller clusters.
Credit: NASA, ESA, and J. Jee (University of California, Davis)

NASA's Hubble Space Telescope has weighed the largest known galaxy cluster in the distant universe and found that it definitely lives up to its nickname: El Gordo (Spanish for "the fat one").

Related Articles


By precisely measuring how much the gravity from the cluster's mass warps images of far-more-distant background galaxies, a team of astronomers has calculated the cluster's mass to be as much as 3 million billion times the mass of our Sun. The Hubble data show that the cluster is roughly 43 percent more massive than earlier estimates based on X-ray and dynamical studies of the unusual cluster.

"It's given us an even stronger probability that this is really an amazing system very early in the universe," said team lead James Jee of the University of California at Davis.

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 galaxy clusters as massive are found in the nearby universe, such as the so-called Bullet Cluster, nothing like this has ever been seen to exist so far back in time, when the universe was roughly half of its current age of 13.8 billion years. The team suspects such monsters 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 huge mass based on observations from 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 very high temperatures of the hot gas between the cluster galaxies.

The challenge was that they noticed that the cluster (catalogued as ACT-CL J0102-4915) looked as if it might have been the result of a titanic collision between a pair of galaxy clusters the researchers describe as "seeing two cannonballs hit 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 that because of the complicated merger state, it left some questions about the reliability of the mass estimates we were making."

"That's where the Hubble data came in," said 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 could be unaccounted for and could potentially suggest that we were actually underestimating the mass." The expectation of "unaccounted energy" comes from the fact that the merger 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 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 Jee.

The team's next step with Hubble will be to try to get a large mosaic image of the cluster. It doesn't fit into Hubble's field of view. It's like looking at a giant's head and shoulders from the side, say researchers. "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.


Story Source:

The above story is based on materials provided by Space Telescope Science Institute. Note: Materials may be edited for content and length.


Journal Reference:

  1. M. James Jee, John P. Hughes, Felipe Menanteau, Cristσbal Sifσn, Rachel Mandelbaum, L. Felipe Barrientos, Leopoldo Infante, Karen Y. Ng. WEIGHING “EL GORDO” WITH A PRECISION SCALE:HUBBLE SPACE TELESCOPEWEAK-LENSING ANALYSIS OF THE MERGING GALAXY CLUSTER ACT-CL J0102–4915 ATz= 0.87. The Astrophysical Journal, 2014; 785 (1): 20 DOI: 10.1088/0004-637X/785/1/20

Cite This Page:

Space Telescope Science Institute. "Monster 'El Gordo' galaxy cluster is bigger than thought." ScienceDaily. ScienceDaily, 3 April 2014. <www.sciencedaily.com/releases/2014/04/140403141831.htm>.
Space Telescope Science Institute. (2014, April 3). Monster 'El Gordo' galaxy cluster is bigger than thought. ScienceDaily. Retrieved October 23, 2014 from www.sciencedaily.com/releases/2014/04/140403141831.htm
Space Telescope Science Institute. "Monster 'El Gordo' galaxy cluster is bigger than thought." ScienceDaily. www.sciencedaily.com/releases/2014/04/140403141831.htm (accessed October 23, 2014).

Share This



More Space & Time News

Thursday, October 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

China Prepares Unmanned Mission To Lunar Orbit

China Prepares Unmanned Mission To Lunar Orbit

Newsy (Oct. 23, 2014) — The mission is China's next step toward automated sample-return missions and eventual manned missions to the moon. Video provided by Newsy
Powered by NewsLook.com
Russian Cosmonauts Kick Off Final Spacewalk of 2014

Russian Cosmonauts Kick Off Final Spacewalk of 2014

Reuters - US Online Video (Oct. 22, 2014) — Russian cosmonauts Maxim Suraev and Alexander Samokutyaev step outside the International Space Station to perform work on the exterior of the station's Russian module. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
Comet Siding Spring Grazes Mars' Atmosphere

Comet Siding Spring Grazes Mars' Atmosphere

Newsy (Oct. 19, 2014) — A comet from the farthest reaches of the solar system passed extremely close to Mars this weekend, giving astronomers a rare opportunity to study it. Video provided by Newsy
Powered by NewsLook.com
Latin America Launches Communications Satellite

Latin America Launches Communications Satellite

AFP (Oct. 17, 2014) — Argentina launches a home-built satellite, a first for Latin America. It will ride a French-made Ariane 5 rocket into orbit, and will provide cell phone, digital TV, Internet and data services to the lower half of South America. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins