The ‘elegant’ solution reveals how the universe got its structure

(Nanowerk News) The universe is full of billions of galaxies, but its distribution in space is far from uniform. Why do we see so much structure in the universe today and how did everything form and grow?

A 10-year survey of tens of thousands of galaxies conducted with the Magellan Baade Telescope at Carnegie’s Las Campanas Observatory in Chile provided a new approach to answer this fundamental mystery. The results, led by Daniel Kelson of Carnegie, are published in Monthly notices from the Royal Astronomical Society (“The severity and nonlinear growth of the structure in the Carnegie-Spitzer-IMACS Redshift Survey”).

“How would you describe the indescribable?” Kelson asks “By taking a whole new approach to the problem.”

“Our tactic provides new and intuitive insights into how gravity drove growth of the structure from the earliest days of the universe,” said co-author Andrew Benson. “This is a direct test based on the observation of one of the pillars of cosmology.”

The Carnegie-Spitzer-IMACS Redshift Survey was designed to study the relationship between the growth of galaxies and the surrounding environment over the past 9 billion years, when the appearances of modern galaxies were defined. The first structure of the universe originated when part of the material thrown out by the Big Bang overcame its trajectory and collapsed on itself, forming groups. A team of Carnegie researchers showed that the denser clumps of matter grew faster, and the less dense clumps grew more slowly. The group’s data revealed the density distribution in the universe over the past 9 billion years. (In the illustration, purple represents low-density regions and red represents high-density regions.) Working backward in time, his findings reveal the density fluctuations (to the right, in purple and blue) that created the earliest structure in the universe. This aligns with what we know about the ancient universe from the Big Bang glow, called the Cosmic Microwave Background (on the right in yellow and green). The researchers achieved their results by examining the distances and masses of nearly 100,000 galaxies, dating back to a time when the universe was only 4.5 billion years old. About 35,000 of the galaxies studied by the Carnegie-Spitzer-IMACS Redshift Study are represented here as small spheres. (Image: illustration courtesy of Daniel Kelson. CMB data is based on observations obtained with Planck, an ESA science mission with instruments and contributions funded directly by ESA Member States, NASA and Canada) (click click on the image to enlarge it)

The first galaxies formed a few hundred million years after the Big Bang, which started the universe as a hot, cloudy soup of extremely energetic particles. As this material expanded outward from the initial explosion, it cooled and the particles coalesced into neutral hydrogen gas. Some patches were denser than others, and eventually their gravity surpassed the outer trajectory of the universe and the material collapsed inward, forming the first clusters of structure in the cosmos.

The differences in density that allowed large and small structures to form in some places and not in others have long been a subject of fascination. But so far, astronomers’ abilities to model how structure grew in the universe in the past 13 billion years faced mathematical limitations.

“The gravitational interactions that occur between all the particles in the universe are too complex to explain with simple mathematics,” said Benson.

So the astronomers used mathematical approximations, which compromised the precision of their models, or large computer simulations that numerically model all interactions between galaxies, but not all interactions that occur between all particles, which was considered too complicated.

“A key objective of our survey was to count the mass present in the stars found in a huge selection of distant galaxies and then use this information to formulate a new approach to understand how structure formed in the universe,” Kelson explained.

The research team, which also included Louis Abramson, Shannon Patel, Stephen Shectman, Alan Dressler, Patrick McCarthy and John S. Mulchaey of Carnegie, as well as Rik Williams, now of Uber Technologies, demonstrated for the first time that the growth of protostructures Individuals can be calculated and then averaged over the entire space.

Doing this revealed that the denser groups grew faster, and the less dense groups grew more slowly.

They were then able to work backward and determine the original distributions and growth rates of the density fluctuations, which would eventually become the large-scale structures that determined the galaxy distributions we see today.

In essence, his work provided a simple but accurate description of why and how density fluctuations grow the way they do in the real universe, as well as the computer-based work that underpins our childhood understanding of the universe. .

“And it’s so simple, with true elegance,” added Kelson.

The findings would not have been possible without the allocation of an extraordinary number of observation nights at Las Campanas.

“Many institutions would not have had the capacity to undertake a project of this scope on their own,” said Director of Observatories John Mulchaey. “But thanks to our Magellan telescopes, we were able to run this survey and create this novel approach to answer a classic question.”

“While there is no doubt that this project required the resources of an institution like Carnegie, our work could not have happened without the enormous amount of additional infrared images that we were able to obtain at Kit Peak and Cerro Tololo, which are part of the National Laboratory. Infrared Optical Astronomy Research Institute, “added Kelson.