Cosmological Results from the Dark Energy Survey

At last the Dark Energy Survey has produced its first cosmological results. The actual papers have not yet hit the arXiv but they have been announced at a meeting in the USA and are linked to from this page.

I’ll jump straight to this one, which shows the joint constraints on S8 which is related to σ8 (a measure of the level of fluctuations in the cosmological mass distribution) via S8= σ8m/0.3)0.5 against the cosmological density parameter, Ωm.

These constraints, derived using DES Y1 measurements of galaxy clustering, galaxy-galaxy lensing, and weak lensing cosmic shear are compared with those obtained from the cosmic microwave background using Planck data, and also combined with them to produce a joint constraint. Following usual practice, the contours are 68% and 95%  posterior probability regions.

The central values of DES and Planck values are different, but the discrepancy is only marginal. Compare this with a an equivalent diagram from a paper I discussed last year.

The KIDS analysis used to produce this plot uses only weak lensing tomography, so you can see that using additional measures reduces the viable region in this parameter space.

It’s great to see new data coming in, but at first sight it seems it is tending to confirm the predictions of the standard cosmological model, rather than providing evidence of departures from it.

Incidentally, this little video shows the extent to which the Dark Energy Survey is a global project, including some of my former colleagues at the University of Sussex!



3 Responses to “Cosmological Results from the Dark Energy Survey”

  1. joergdietrich Says:

    The full papers are already available on the second link in this blog post. Enjoy reading! The y-axis actually shows S_8 = \sigma_8(\Omega_m/0.3)^0.5 as sigma_8 is strongly degenerate with Omega_m.

    • telescoper Says:

      Thanks. I have included the definition now. I didn’t see the links to the papers originally but have now found them and added.

  2. As you mentions, PLANCK and DES are exploring very different timescales. Could the ‘discrepancy’ point to some kind of evolution of the parameters? (of course, the discrepancy don’t warrant such a claim, but just out of interest…)

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