Data: 23.06.2016

Palestrante: Dr. Joel Primack (University of California)

Link: https://youtu.be/ID8WtT6C3_k

Resumo: Large-scale simulations track the evolution of structure in the ΛCDM universe of dark energy and cold dark matter on scales of billions of light years, and cosmological zoom-in simulations model how individual galaxies evolve through the interaction of baryonic matter and dark matter. New large-scale simulations based on the latest cosmological parameters are being used in novel ways to predict the rate of star formation and the distribution of galaxies with various properties across cosmic time. Astronomers used to think (1) that galaxies are a combination of stellar disks and spheroids, like nearby galaxies; (2) that galaxies are mostly smooth (the largest lumps in the Milky Way are globular clusters and giant molecular clouds, each with a maximum mass about a million times the mass of the sun); and (3) that galaxies mostly grow in radius as they grow in mass. New discoveries from CANDELS, the biggest-ever Hubble Space Telescope program, have shown that all three are wrong! Instead, by comparing zoom-in galaxy simulations with CANDELS observations, we have found that (1) most galaxies start elongated (zucchini-shaped) and only later become rounder as their centers become dominated by baryonic matter; (2) most star-forming galaxies in the early universe have giant clumps of stars with masses of a hundred million solar masses or more; and (3) forming galaxies sometimes undergo a period of rapid shrinkage in the radius that encloses half their light as they grow in mass, a process that we call “compaction”. New telescopes including James Webb Space Telescope will no doubt lead to further insights on structure formation in the universe.