The Dark Energy Survey (DES) consortium has released the results of its first year of activity and they confirm that our current model of the universe is pretty accurate. The international collaboration studied the distribution of 26 million galaxies and how they have changed over the past 7 billion years.
The series of papers were presented this week at a meeting at Fermilab and covered several different aspects of the survey and its results, including a precise map of the projected density of dark matter spanning several billion light-years.
DES also established precise measurements for several key cosmological parameters. They compared these values with what the European Space Agency’s Planck Satellite estimated from its observations of the cosmic microwave background, and they are in broad agreement.
"While Planck looked at the structure of the very early universe, DES has measured structures that evolved much later," DES member Daniel Gruen, from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), said in a statement. "The growth of these structures from the early ages of the universe until today agrees with what our models predict, showing that we can describe cosmic evolution very well."
The standard cosmological model, known as Lambda-CDM, requires the universe to be composed of dark matter and dark energy. Dark matter is a type of matter that doesn’t interact with light, while dark energy is a mysterious substance that pushes the universe to expand with an acceleration.
We have been measuring their effects for decades, but their true nature remains elusive. For this reason, researchers are focusing their efforts on increasing the precision of these measurements. By constraining our parameters, we might be able to work out their properties and whether or not they change over time.
"Within an error bar of less than 5 percent, the combined Planck and DES results are consistent with Lambda-CDM," said Risa Wechsler, a founding member of DES at the KIPAC. "This also means that, so far, we don't need anything but a constant form of dark energy to describe the expansion history of the universe."
"For the first time, the precision of key cosmological parameters coming out of a galaxy survey is comparable to the ones derived from measurements of the cosmic microwave background," added Wechsler. "This allows us to test our models independently and combine both approaches to obtain parameter values with unprecedented precision."
The DES consortium plans to run the survey for four more years. These papers are already raising questions in the astrophysical community, so it will be exciting to see what new analyses and interpretations they inspire.