Understanding the "cold spot" in the cosmic microwave background

Sat, 15 Jan 2022 18:43:39 GMT
Space Daily

Batavia IL (SPX) Jan 14, 2022 After the Big Bang, the universe, glowing brightly, was opaque and so...

Scientists used data collected by the Dark Energy Survey to confirm the existence of one of the largest supervoids known to humanity, the Eridanus supervoid, as reported in a paper published in December 2021.

Between these clusters of galaxies are voids: vast regions of space that contain fewer galaxies, and thus less ordinary matter, and less dark matter than exists within the galaxy clusters.

Mapping dark matter To make this discovery, scientists used Dark Energy Survey data to create a map of dark matter in the same direction as the CMB Cold Spot, by observing the effect of gravitational lensing.

The new map shows there is a matching underdensity of invisible dark matter.

Using voids to understand dark energy The Dark Energy Survey is an international effort to understand the effect dark energy has on the acceleration of the universe.

The Dark Energy Survey documents hundreds of millions of galaxies, supernovae and patterns within the cosmic web, using a 570-Megapixel digital camera, called the DECam, high in the Chilean Andes.

At the largest scales of the universe, there is a tug-of-war between the gravitational forces and the expansion of the universe from dark energy, making some of the voids between galactic clusters deeper.

Open questions Although the new result confirms that the Eridanus supervoid is gigantic, it still is not sufficient to explain the discrepancy between the predictions of the current standard cosmological model used to predict the behavior of dark energy-known as the Lambda Cold Dark Matter model-and the observed change in temperature in the Cold Spot that can be attributed to the supervoid's effect on photons from the CMB. "Having the coincidence of these two individually rare structures in the cosmic web and in the CMB is basically not enough to prove causality with the scientific standard," said Andras Kovacs, the lead researcher on this project.

The latter would indicate a greater influence of dark energy on the universe and possibly faster cosmic expansion.

The Dark Energy Survey team observed that the lensing signal from the Eridanus supervoid is slightly weaker than expected.