HEAPOW: Web of Darkness (2010 Feb 08)

Find out the latest thinking about our universe.
User avatar
bystander
Apathetic Retiree
Posts: 20066
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

HEAPOW: Web of Darkness (2010 Feb 08)

Post by bystander » Tue Feb 09, 2010 4:22 pm

Image HEAPOW: Web of Darkness (2010 Feb 08)
Even though astronomers believe the Universe to be constructed of Dark Matter, no one really knows what Dark Matter is. It apparently only interacts through its gravitational attraction with normal matter, so that even its simplest properties are mostly unknown: does it change with time, do you have more dark matter if you have more normal matter, etc. The seeming impossibility of characterizing the invisible makes studies of Dark Matter properties daunting, but astronomers are nothing if not resolute. The image above shows one of the latest attempts to study Dark Matter. This image shows the galaxy density in the Cosmological Evolution Survey (COSMOS) field, with colors representing the redshift distance of galaxies in the image. These galaxies span a wide range of redshift, from a redshift of 0.2 (shown in blue) to 1 (red). Astronomers can study the galaxy clusters in the COSMOS survey and determine the total amount of matter, both the visible and Dark forms, using a statistical measure of the bending of light by the space-time distortion of the gravitating matter. The contours in pink show X-ray brightness profiles of the clusters as measured by the XMM-Newton X-ray Observatory. The X-ray data are vital to measure the total mass of only the normal matter held bound by a cluster. Using the large span of redshift distance in the COSMOS survey, astronomers hope to constrain how Dark Matter evolves with the Universe, one step closer to solving its mystery.
XMM-Newton traces dark matter in faint, distant galaxy groups
<< Previous HEAPOW High Energy Astrophysics
Picture of the Week
Next HEAPOW >>
[/b]

User avatar
bystander
Apathetic Retiree
Posts: 20066
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

UT: Dark Matter in Distant Galaxy Groups Mapped

Post by bystander » Sun Feb 21, 2010 6:19 pm

Dark Matter in Distant Galaxy Groups Mapped for the First Time
Universe Today - 2010 Feb 21
Dark matter (actually cold, dark – non-baryonic – matter) can be detected only by its gravitational influence. In clusters and groups of galaxies, that influence shows up as weak gravitational lensing, which is difficult to nail down. One way to much more accurately estimate the degree of gravitational lensing – and so the distribution of dark matter – is to use the x-ray emission from the hot intra-cluster plasma to locate the center of mass.

And that's just what a team of astronomers have recently done … and they have, for the first time, given us a handle on how dark matter has evolved over the last many billion years.

User avatar
bystander
Apathetic Retiree
Posts: 20066
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

ESA: XMM-Newton traces dark matter in distant galaxy groups

Post by bystander » Sun Feb 21, 2010 6:23 pm

XMM-Newton traces dark matter in faint, distant galaxy groups
ESA XMM-Newton - 2010 Jan 20
Observations of faint and distant galaxy groups made with the European Space Agency's XMM-Newton observatory have been used to probe the evolution of dark matter. The results of the study are reported in the 20 January issue of The Astrophysical Journal.

Dark matter is a mysterious, invisible constituent of the Universe which only reveals itself through its gravitational influence. Understanding its nature is one of the key open questions in modern cosmology. In one of the approaches used to address this question astronomers use the relationship between mass and luminosity that has been found for clusters of galaxies which links their X-ray emissions, an indication of the mass of the ordinary (baryonic) matter alone, and their total masses (baryonic plus dark matter) as determined by gravitational lensing.

To date the relationship could only be established for nearby clusters. New work by an international collaboration, including the Max Planck Institute for Extraterrestrial Physics (MPE), the Laboratory of Astrophysics of Marseilles (LAM), and Lawrence Berkeley National Laboratory (Berkeley Lab), has made major progress in extending the relationship to more distant and smaller structures than was previously possible.

The Code
2+2=5
Posts: 913
Joined: Sat Mar 07, 2009 6:39 pm
AKA: Swainy
Location: The Earth, The Milky Way, Great Britain

Re: HEAPOW: Web of Darkness (2010 Feb 08)

Post by The Code » Mon Feb 22, 2010 5:59 pm

Thanks For posting these bystander.

Mark
Always trying to find the answers