From the article;
"So what does this tell us? The model of the lens outlines the (projected 2D) mass profile of the cluster – which doesn’t seem to agree with numerical simulations for clusters, assuming a standard ΛCDM cosmology. The mass concentration in the center of the cluster is higher than predicted, a result that has also been found for other massive clusters studied with gravitational lensing. This implies that we’re either missing some physics in our simulations, or we may need to modify our cosmological model."
Let me see if I have this right.
They process the images based on the assumption that the "blue galaxies" are lensed by the "foreground" cluster.
At a short sentence summary level, yes.
They convolve the images to some shape and measure the mass concentration in the images.
The Discovery blog entry summarises what's involved better; they
start with a model of the lens (i.e. the 2D distribution of the mass), and tweak it until they have consistency.
This leads to
predictions of where, and what shape, other lensed images should be found. They take a deeper look at the data, discover that there are, indeed, many other, quite faint, lensed images. These are then input to the model, which is iterated one more time.
A technical note: the number of degrees of freedom (crudely, how much tweaking they can do) is much less than number of the independent data points ... this means that if there is no distribution of mass acting like a lens, or if mass/gravity doesn't bend light as described by GR, or if the background galaxies are at different distances, or ... then there will be an inconsistent result.
If this does not match the ΛCDM model then they say there is dark matter there?
You rather badly misunderstood that part.
The lens reconstruction/mass distribution modelling owes nothing to ΛCDM models!
Simulations based on ΛCDM models, such as the Millennium simulation, are simplifications of how part of the universe evolved, over a particular period.
AFAIK, no such simulation has attempted to model the evolution of the universe with the electromagnetic, weak, and strong forces accounted for.
If clusters seem to have isodense cores, as at least some dwarf galaxies do too, perhaps this is an indication that some key physical processes have been overlooked, or ignored? Or perhaps ΛCDM models need to be re-examined?
That is insane. Religion. Too much faith in their beautiful equations. Incorrect use of a computer. Danger Will Robinson.....
This I do not understand at all.
If it were 'religion', with lots of 'faith', then why would astronomers, astrophysicists, and cosmologists be happy with papers like Zitrin & Broadhurst's? Why would they bother spending hundreds of hours of time on the worlds' best telescopes, to take ever better and deeper images?
I would choose option B except I dont think that modify is a strong enough word. I would choose "falsify"..
And you'd be in good company (well, 'modify'-wise).
Your post, that I am quoting, seems to reflect the 'naive falsificationism' which even its creator (Popper) was at pains to point out would be ridiculous way to do science ...
To sum up: here we see science at its best, working in exactly the way it's supposed to. Or, if you prefer, ΛCDM theory: the very antithesis of scientific woo.
