29 articles report various aspects of the results of a major cosmological research on the largest sample of galaxies – 226 million of them – ever observed to produce the most accurate measurements of the composition and growth of the universe. More than 400 scientists from the DES (Dark Energy Survey) Collaboration used images captured by the Dark Energy Camera in the first three years of the program, which started in 2013, to obtain results. The goal is to improve our knowledge of the universe, in particular, the nature of dark matter and dark energy.
Gravitational effects detected during multiple observations and the discovery that the expansion of the universe is accelerating led, respectively, to the hypothesis of the existence of dark matter and dark energy. However, the many attempts made to obtain direct evidence of their existence have so far failed. Alternative models have been offered for the observed effects but, again, no one has been able to bring direct evidence of their validity. While discussions continue, new astronomical observations are being conducted to bring more detailed information, including the one from DES.
DES’s deep field images show a total of 226 million galaxies spanning around 7 billion light-years showing how the structure of the universe evolved over the past 7 billion years. This means for example examining the distribution of galaxies in a cosmic structure that forms a kind of web in which the galaxies are joined by filaments. Gravitational bonds are the ones that can show the effects attributed to dark matter. Gravitational lenses, the distortions generated when light is bent by gravity, are another phenomenon that can show the effects attributed to dark matter. Gravitational lenses formed the basis of a dark matter map presented by the DES Collaboration nearly 4 years ago.
This large cosmological survey concerns the relatively recent universe but scientists have a reference point in the map created thanks to measurements of the early universe of ESA’s Planck Surveyor satellite. The results obtained by the DES Collaboration showed from the first analyzes a good agreement with the predictions based on the data concerning the early universe and that’s still true after these new analyzes. However, the recent universe looks slightly more homogeneous than was predicted. The significance and the possible importance of this discovery need to be assessed with further investigation.
The DES Collaboration ended its observations in 2019 but it will take some time to have an analysis of all the data collected over the six years of the survey. In these cases, partial analyzes are helpful because they allow to develop the various software tools and in general everything needed for the job. The final analysis will allow obtaining even more precise information on dark matter and dark energy. It’s one of the crucial goals of this great survey that will help uncover their nature and test alternative models of the nature of the cosmos.