Imaging the distribution of dark matter-anyone want to expand on this?


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Their method sounds good for the SKA - which isn't built yet.

Hans de Vries

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There was an IBM press release on the Square Kilometer Array (SKA) radio
telescope just last week:

IBM said:
Astron and IBM Team To Help Research the First Origins Of The Universe

ASTRON and IBM to Collaborate on a New Customized Chip Design to Help Build the World's Largest Radio Astronomy Telescope.

Amsterdam, The Netherlands and Armonk, NY - 06 Dec 2006:
ASTRON, one of the world's leading astronomy research organizations, today announced a new collaborative agreement with IBM (NYSE: IBM) focusing on the design, engineering and manufacturing of customized, high performance analogue and mixed signal processing chips. The high performance, low power usage customized chips will be used in thousands of antennas as part of ASTRON's project to build a new prototype radio telescope called SKADS/EMBRACE, which will be the precursor for the world’s largest radio astronomy telescope, the Square Kilometer Array (SKA) radio telescope. Financial terms are not being disclosed.

Regards, Hans


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the young researcher who made the map, Stefan Hilbert, is at the Max Planck Instutite for Astrophysics at Garching.
He was using an idea of how to "see" dark matter which was proposed by Metcalf and White, also at MPI Garching, in this paper:

A map was produced showing the [dark matter] mass distribution over a patch of sky about one quarter of the area of the Full Moon.

The method looks for distortions in the background of ancient neutral hydrogen (21 cm) radiation, from before the galaxies coagulated ("curdled"), at a time when the structure of the universe and the distribution of matter were more uniform.
Different layers of 21 cm radiation going back in time different amounts can be distinguished by their redshift.
The distortion of each layer is used to reconstruct the distribution of dark matter between us and the source of radiation.

The map or image of dark matter seems to have been synthesized from many separate observations by radio telescopes of this hydrogen radiation.
It is in a sense a "mosaic" because he used a computer to combine many different observations into one big image---that is AS IF it had been made by a very large radio telescope (larger than any now available).

For us in the "Beyond Standard" context, information about dark energy and dark matter is of interest because
either the standard model of gravity (Gen Rel) has to be modified in how it behaves at long distance---to account for DM and DE effects---
or the standard matter model has to be supply, or be modified to supply, particles and fields to account for these effects.
The observed DM and DE effects present one of the main challenges which motivates beyond standard extensions of Gen Rel and QFT.
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It seems to be a widely spread misconception that the bending of light provides "direct" evidence of dark matter. An observation of lightbending only indicates that something has to exist which causes the bending (which does not contain so much information :tongue: ). If one then ASSUMES that the lightbending is due to gravitation, one could infer the presence of unseen (dark) matter. Direct evidence of dark matter should be that one can interact with it, study it in particle accelerators, etc.
Personally, I don't believe in dark matter at all (see ). The desperate and incredable research going on in this field will later be considered as the biggest historical scientific blunder of all times.
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