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:
http://arxiv.org/abs/astro-ph/0611862/
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).
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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.
). 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.