Featured Research

from universities, journals, and other organizations

Galaxy Cluster Surveys May Help Explain "Dark Energy" In The Universe

Date:
April 24, 2002
Source:
University Of Illinois At Urbana-Champaign
Summary:
The universe appears to be permeated with an invisible force – dark energy – that is pushing it apart faster and faster. By conducting redshift surveys of galaxy clusters, astronomers hope to learn more about this mysterious force, and about the structure and geometry of the universe.

ALBUQUERQUE, N.M. — The universe appears to be permeated with an invisible force – dark energy – that is pushing it apart faster and faster. By conducting redshift surveys of galaxy clusters, astronomers hope to learn more about this mysterious force, and about the structure and geometry of the universe. “Galaxy clusters consist of thousands of galaxies gravitationally bound into huge structures,” said Joseph Mohr, a professor of astronomy at the University of Illinois. “Because of the expansion of the universe, the clusters appear denser at larger redshifts, when the universe was younger and denser.”

Galaxy cluster surveys that probe the high-redshift universe can potentially provide a wealth of information about the amount and nature of both dark matter and dark energy, said Mohr, who will present the results of an ongoing study of galaxy clusters at a meeting of the American Physical Society, to be held in Albuquerque, N.M., April 20-23.

“Till now, galaxy clusters have only been used to study the dark matter component of the universe,” Mohr said. “We would measure the total mass in a galaxy cluster, and then determine the fraction of mass that was ordinary, baryonic matter.”

Those measurements have shown there is insufficient baryonic and dark matter to account for the geometry of the universe. Astronomers now believe the universe is expanding at ever-increasing speed, and is dominated by a mysterious dark energy that must be doing the pushing.

“The next step is to try to figure out some of the specifics of the dark energy, such as its equation of state,” Mohr said. “By mapping the redshift distribution of galaxy clusters, we should be able to measure the equation of state of dark energy, which would provide some important clues to what it is and how it came to be.”

Mohr is using data collected by NASA’s Chandra X-ray Observatory to study scaling relations – such as the relationship between mass and luminosity or size – of galaxy clusters and how they change with redshift. “These scaling relations are expected to evolve with redshift, reflecting the increasing density of the universe at earlier times,” Mohr said.

In particular, Mohr – in collaboration with John Carlstrom at the University of Chicago and scientists at the University of California and Harvard Smithsonian Center for Astrophysics – is studying the effect that hot electrons within galaxy clusters have on the cosmic microwave background, the afterglow of the big bang.

Galaxy clusters are filled with dark matter, galaxies and hot gas. Electrons in the gas scatter off the protons and produce X-rays. The emission of X-rays diminishes with higher redshift, because of the larger distances involved.

“There also is a tendency for the electrons to give some of their energy to the photons of the cosmic microwave background, which causes the blackbody spectrum to shift slightly,” Mohr said. “The resulting distortion – called the Sunyaev-Zeldovich effect – appears as a cold spot on the cosmic microwave background at certain frequencies. Because this is a distortion in the spectrum, however, it doesn’t dim with distance like X-rays.”

By comparing the X-ray emission and the Sunyaev-Zeldovich effect, Mohr can study even faint, high-redshift galaxy clusters that are currently inaccessible by other means. Such measurements, correlating galaxy cluster redshift distribution, structure and spatial distribution, should determine the equation of state of dark energy and, therefore, help define the essence of dark energy.

“Within the context of our standard structure formation scenario, galaxy surveys provide measurements of the geometry of the universe and the nature of the dark matter and dark energy,” Mohr said. “But, to properly interpret these surveys, we must first understand how the structure of galaxy clusters are changing as we look backward in time.”


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "Galaxy Cluster Surveys May Help Explain "Dark Energy" In The Universe." ScienceDaily. ScienceDaily, 24 April 2002. <www.sciencedaily.com/releases/2002/04/020422073037.htm>.
University Of Illinois At Urbana-Champaign. (2002, April 24). Galaxy Cluster Surveys May Help Explain "Dark Energy" In The Universe. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2002/04/020422073037.htm
University Of Illinois At Urbana-Champaign. "Galaxy Cluster Surveys May Help Explain "Dark Energy" In The Universe." ScienceDaily. www.sciencedaily.com/releases/2002/04/020422073037.htm (accessed July 31, 2014).

Share This




More Space & Time News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Supply Ship Takes Off for International Space Station

Supply Ship Takes Off for International Space Station

AFP (July 30, 2014) The European Space Agency's fifth Automated Transfer Vehicle (ATV-5) is takes off to the International Space Station on an Ariane 5 rocket from French Guiana. Duration: 00:34 Video provided by AFP
Powered by NewsLook.com
Raw: Rocket Launches Into Space With Cargo Ship

Raw: Rocket Launches Into Space With Cargo Ship

AP (July 30, 2014) Arianespace launched a rocket Tuesday from French Guiana carrying a robotic cargo ship to deliver provisions to the International Space Station. (July 30) Video provided by AP
Powered by NewsLook.com
In Virginia, the Rise of a New Space Coast

In Virginia, the Rise of a New Space Coast

AP (July 30, 2014) Every summer, tourists make the pilgrimage to Chincoteague Island, Va. to see wild ponies cross the Assateague Channel. But, it's the rockets sending to supplies to the International Space Station that are making this a year-round destination. (July 30) Video provided by AP
Powered by NewsLook.com
Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Newsy (July 27, 2014) The satellite is back under ground control after a tense few days, but with a gecko sex experiment on board, the media just couldn't help themselves. Video provided by Newsy
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:
from the past week

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