Galaxy formation

This image is a snapshot taken from a cosmology simulation by Brian O'Shea (Theoretical Astrophysics Group, Los Alamos National Laboratory) and Michael Norman (University of California, San Diego). The calculation follows the evolution of a region of the universe 250 million light years on a side, starting from only 16 million years after the Big Bang and ending at the present day, 13.7 billion years later. The purpose of this computation was to understand how a galaxy like our own forms and evolves over the lifetime of the universe. The calculation used a technique called "adaptive mesh refinement," which allows researchers to follow objects evolving on a large range of spatial and temporal scales while maximizing computational efficiency. Dark matter and the evolution of gas are followed separately, and a prescription for star formation and supernovae are also used.

This image shows two galaxies that are in the midst of a very complicated merger. Stars are shown as white streaks, and gas is shown in orange. When galaxies merge, they produce a halo of stars around them. Some will eventually settle back into the disk of the galaxy, and others will be jettisoned into intergalactic space. The "tidal tails" of gas are ejected from the galaxies during their closest point of approach and will eventually fall back onto the new galaxy.

The image on the back cover shows the final stages of a merger of two galaxies into a larger one. A tidal tail of gas and stars (orange cloud and white streaks, respectively) is formed during the merger. This tail is similar to features seen by the Hubble Space Telescope in merging galaxies such as the Antennae Galaxies and will eventually fall back onto the galaxy.

This work was supported by NASA, the National Science Foundation, and the Department of Energy.

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Galaxy formation