Subscribe free to our newsletters via your
. 24/7 Space News .

Subscribe free to our newsletters via your

In galaxy clustering, mass may not be the only thing that matters
by Staff Writers
Pittsburgh PA (SPX) Jan 26, 2016

Density maps of galaxy cluster distribution.

An international team of researchers, including Carnegie Mellon University's Rachel Mandelbaum, has shown that the relationship between galaxy clusters and their surrounding dark matter halo is more complex than previously thought.

The researchers' findings, published in Physical Review Letters are the first to use observational data to show that, in addition to mass, a galaxy cluster's formation history plays a role in how it interacts with its environment.

There is a connection between galaxy clusters and their dark matter halos that holds a great deal of information about the universe's content of dark matter and accelerating expansion due to dark energy. Galaxy clusters are groupings of hundreds to thousands of galaxies bound together by gravity, and are the most massive structures found in the universe.

These clusters are embedded in a halo of invisible dark matter. Traditionally, cosmologists have predicted and interpreted clustering by calculating just the masses of the clusters and their halos.

However, theoretical studies and cosmological simulations suggested that mass is not the only element at play - something called assembly bias, which takes into account when and how a galaxy cluster formed, also could impact clustering.

"Simulations have shown us that assembly bias should be part of our picture," said Mandelbaum, a member of Carnegie Mellon's McWilliams Center for Cosmology. "Confirming this observationally is an important piece of understanding galaxy and galaxy cluster formation and evolution."

In the current study, the research team, led by Hironao Miyatake, Surhud More and Masahiro Takada of the Kavli Institute for the Physics and Mathematics of the Universe, analyzed observational data from the Sloan Digital Sky Survey's DR8 galaxy catalog. Using this data, they demonstrated that when and where galaxies group together within a cluster impacts the cluster's relationship with its dark matter environment.

The researchers divided close to 9,000 galaxy clusters into two groups based on the spatial distribution of the galaxies in each cluster. One group consisted of clusters with galaxies aggregated at the center and the other consisted of clusters in which the galaxies were more diffuse.

They then used a technique called gravitational lensing to show that, while the two groups of clusters had the same mass, they interacted with their environment much differently. The group of clusters with diffuse galaxies were much more clumpy than the group of clusters that had their galaxies close to the center.

"Measuring the way galaxy clusters clump together on large scales is a linchpin of modern cosmology. We can go forward knowing that mass might not be the only factor in clustering," Mandelbaum said.

Additional authors of the study include: David N. Spergel, Princeton University; Eli S. Rykoff, Kavli Institute for Particle Astrophysics and Cosmology; and Eduardo Rozo, University of Arizona.


Related Links
Carnegie Mellon University
The Physics of Time and Space

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Previous Report
LISA Pathfinder arrives at its worksite
Paris (ESA) Jan 25, 2016
After a six-week journey, LISA Pathfinder arrived at its destination today, an orbit around a point of balance in space where it will soon start testing technologies crucial for exploring the gravitational Universe. LISA Pathfinder is testing the key elements that could be used for a future mission to detect gravitational waves - ripples in spacetime predicted by Albert Einstein in his Gen ... read more

Russia postpones manned Lunar mission to 2035

Audi joins Google Lunar XPrize competition

Lunar mission moves a step closer

Momentum builds for creation of 'moon villages'

Opportunity rock abrasion tool conducts two rock grinds

Opportunity Abrasion Tool Conducts Two Rock Grinds

Curiosity gets a good taste of scooped, sieved sand

Rover uses Rock Abrasion Tool to grind rocks

Voyager Mission Celebrates 30 Years Since Uranus

Engineers Mark Completion of Orion's Pressure Vessel

2016 Goals Vital to Commercial Crew Success

Space: The here-and-now frontier

China aims for the Moon with new rockets

China shoots for first landing on far side of the moon

Chinese Long March 3B to launch Belintersat-1 telco sat for Belarus

China Plans More Than 20 Space Launches in 2016

Astronaut Scott Kelly plays ping pong with water

Japanese astronaut learned Russian to link two nations

NASA, Texas Instruments Launch mISSion imaginaTIon

Water in US astronaut's helmet cuts short Briton's 1st spacewalk

Roscosmos Approves Delay of Eutelsat 9B Launch Due to Bad Weather

Assembly begins on 2nd Ariane 5 launcher for 2016

Ariane 5 is readied for an Arianespace leading customer Intelsat

EpicNG satellite installed on Ariane 5 for launch

Follow A Live Planet Hunt

Lab discovery gives glimpse of conditions found on other planets

Nearby star hosts closest alien planet in the 'habitable zone'

ALMA reveals planetary construction sites

New insights into the supercritical state of water

It's a 3-D printer, but not as we know it

Microsoft donates cloud computing 'worth $1 bn'

Research reveals mechanism for direct synthesis of hydrogen peroxide

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.