Cosmic Structure

Cosmic Structure

How did all of the structure we see in the Universe originate from the nearly uniform conditions of its early moments? How do the first stars and galaxies form, and how do galaxies evolve over time to create the complexity we see today?  How can we measure the evolution of cosmic structure, what do we learn from how it evolves, and how might it evolve in the far future?

Cosmologists at KIPAC study the structure of the Universe from nearby galaxies and their satellites to the distribution of galaxies on the largest scales across the Universe.  By studying the structure of the Universe, we can learn how the Universe developed from its initial state and how the galaxies formed, grew, and merged with one another into the diverse population we can see today.

Large Scale Structure

Galaxies are everywhere we look in the sky. Their seemingly random placements are in fact part of a massive interconnected structure called the cosmic web. Hidden in their spatial distribution is a treasure trove of information about the past, present, and future fate of the Universe. KIPAC's cosmologists use both computer simulations and pen-and-paper calculations to try to figure out how the observed distribution of galaxies came about. They also study how this distribution depends on the properties of dark matter, dark energy, and other properties of the Universe, and develop new statistical tools to extract all of the information available in this distribution.

Observational cosmologists at KIPAC are studying the formation of this cosmic web, observing millions of galaxies as well as the largest bound structures in the Universe, galaxy clusters, with optical surveys including DES, DESI and the Vera Rubin Observatory LSST. KIPAC scientists combine these observations with measurements of the cosmic microwave background (CMB), which reveal the initial seeds of structure, formed in the early Universe, that led to the creation of the galaxies we see today.

Galaxy Formation

Research at KIPAC is revealing the lifecycle of galaxies: how galaxies were born in the darkness of the early Universe, how their different components interact as they live and grow, and how they die. KIPAC scientists are studying early galaxies with computer simulations to understand the formation of the first stars and galaxies, and use a combination of observations and theoretical models to figure out how the supermassive black hole in the center of each galaxy controls the galaxy’s growth. KIPAC researchers are at the forefront of modeling the connection between galaxies and the halos of dark matter surrounding them and of using galaxies as laboratories to test the nature of dark matter and other cosmological theories.

Galaxy Clusters

Clusters, containing thousands of galaxies, held together by the force of gravity, are the largest bound objects in the Universe. At KIPAC, astrophysicists are studying galaxy clusters to better understand how the largest structures in the Universe are assembled, the interplay of the galaxies, the hot intracluster medium that surrounds them and dark matter, and the roles the supermassive black holes in the central galaxies play in the growth of the cluster and the galaxies.

Gravitational Lensing

As light travels across the Universe from distant galaxies, its path is bent around massive objects, leading to gravitational lensing. At KIPAC, cosmologists are able to measure how gravitational lensing distorts the shapes of galaxies to create maps locating all of the matter in the Universe. This technique is a particularly powerful tool to reveal the distribution of the dark matter that dominates the Universe’s mass, and to trace the Universe’s expansion and growth of structure over time.

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