Probing dark energy with clusters: "Russian doll" galaxy clusters reveal information about dark energy

April 28, 2016
Credit: X-ray: NASA/CXC/Univ. of Alabama/A. Morandi et al; Optical: SDSS, NASA/STScI

These four galaxy clusters were part of a large survey of over 300 clusters used to investigate dark energy, the mysterious energy that is currently driving the accelerating expansion of the Universe, as described in our latest press release. In these composite images, X-rays from NASA's Chandra X-ray Observatory (purple) have been combined with optical light from the Hubble Space Telescope and Sloan Digital Sky Survey (red, green, and blue).

Researchers used a novel technique that takes advantage of the observation that the outer reaches of galaxy clusters, the largest structures in the universe held together by gravity, show similarity in their X-ray emission profiles and sizes. That is, more massive clusters are simply scaled up versions of less massive ones, similar to Russian dolls that nest inside one another.

The amount of matter in the Universe, which is dominated by the unseen substance called dark matter, and the properties of (what astronomers call cosmological parameters) affect the rate of expansion of the Universe and, therefore, how the distances to objects change with time. If the cosmological parameters used are incorrect and a cluster is inferred to be traveling away faster than the correct value, then a cluster will appear to be larger and fainter due to this "Russian doll" property. If the cluster is inferred to be traveling away more slowly than the correct value, the cluster will be smaller and brighter than a cluster according to theory.

These latest results confirm earlier studies that the amount of dark energy has not changed over billions of years. They also support the idea that dark energy is best explained by the "cosmological constant," which Einstein first proposed and is equivalent to the energy of empty space.

The galaxy clusters in this large sample ranged in distance from about 760 million to 8.7 billion light years from Earth, providing astronomers with information about the era where dark energy caused the once-decelerating expansion of the Universe to accelerate.

The X-ray emission in the outer parts of is faint because the gas is diffuse there. To deal with this issue in this study, the X-ray signal from different clusters was added together. Regions near the centers of the clusters are excluded from the analysis because of large differences between the properties of different clusters caused by supermassive black hole outbursts, the cooling of gas and the formation of stars.

A paper describing these results by Andrea Morandi and Ming Sun (University of Alabama at Huntsville) appeared in the April 11th, 2016 issue of the Monthly Notices of the Royal Astronomical Society journal and is available online. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Explore further: Image: Hubble looks into a cosmic kaleidoscope

Related Stories

Image: Hubble looks into a cosmic kaleidoscope

March 28, 2016

At first glance, this cosmic kaleidoscope of purple, blue and pink offers a strikingly beautiful—and serene—snapshot of the cosmos. However, this multi-colored haze actually marks the site of two colliding galaxy clusters, ...

Chandra finds remarkable galactic ribbon unfurled

December 22, 2015

An extraordinary ribbon of hot gas trailing behind a galaxy like a tail has been discovered using data from NASA's Chandra X-ray Observatory. This ribbon, or X-ray tail, is likely due to gas stripped from the galaxy as it ...

Dark matter is darker than once thought

March 27, 2015

This panel of images represents a study of 72 colliding galaxy clusters conducted by a team of astronomers using NASA's Chandra X-ray Observatory and Hubble Space Telescope. The research sets new limits on how dark matter ...

Telescopes combine to push frontier on galaxy clusters

March 11, 2016

Galaxy clusters are enormous collections of hundreds or even thousands of galaxies and vast reservoirs of hot gas embedded in massive clouds of dark matter, invisible material that does not emit or absorb light but can be ...

Recommended for you

JPL deploys a CubeSat for astronomy

December 8, 2017

Tiny satellites called CubeSats have attracted a lot of attention in recent years. Besides allowing researchers to test new technologies, their relative simplicity also offers hands-on training to early-career engineers.

Black holes' magnetism surprisingly wimpy

December 7, 2017

Black holes are famous for their muscle: an intense gravitational pull known to gobble up entire stars and launch streams of matter into space at almost the speed of light.

NASA Mars rover team's tilted winter strategy works

December 7, 2017

NASA's senior Mars rover, Opportunity, has just passed the shortest-daylight weeks of the long Martian year with its solar panels in encouragingly clean condition for entering a potential dust-storm season in 2018.

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

liquidspacetime
1 / 5 (1) Apr 28, 2016
Dark matter fills 'empty' space. Dark matter strongly interacts with matter. Dark matter is displaced by matter.

[0903.3802] The Milky Way's dark matter halo appears to be lopsided

"the emerging picture of the dark matter halo of the Milky Way is dominantly lopsided in nature."

The Milky Way's halo is not a clump of dark matter traveling along with the Milky Way. The Milky Way's halo is lopsided due to the matter in the Milky Way moving through and displacing the dark matter, analogous to a submarine moving through and displacing the water.

What physicists mistake for the density of the dark matter is actually the state of displacement of the dark matter. Physicists think they are determining the density of the dark matter by how much it and the matter curve spacetime. What they fail to realize is the state of displacement of the dark matter is curved spacetime.
liquidspacetime
1 / 5 (1) Apr 28, 2016
Black holes banish matter into cosmic voids
http://www.spaced...999.html

"Some of the matter falling towards the [supermassive black] holes is converted into energy. This energy is delivered to the surrounding gas, and leads to large outflows of matter, which stretch for hundreds of thousands of light years from the black holes, reaching far beyond the extent of their host galaxies."

At the scale of our Universe the energy described above is dark energy. A Universal black hole is powering the Universal lobe we exist in.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.